TM 11-2651

D E P A R T M E N T O F T H E A R M Y T E C H N I C A L M A N U A L

ANTENNA GROUPS

AN/GRA-4

AND

AN/GRA-12

This copy is a reprint which includes currentpages from Changes 1 through 3

WARNING

DANGEROUS VOLTAGES EXIST ON THE ANTENNA WHEN IN OPERATION

Before working on any part of the antenna, be certain that all powerhas been turned off.

DON'T TAKE CHANCES!

TM 11-2651TO 31R2-2GRA-101

*C 1DEPARTMENT OF THE ARMY TECHNICAL MANUALDEPARTMENT OF THE AIR FORCE TECHNICAL ORDERANTENNA GROUPS AN/GRA-4 AND AN/GRA-12

TECHNICAL MANUAL DEPARTMENTS OF THE ARMYNo. 11-2651 AND THE AIR FORCETECHNICAL ORDERNo. 31R2-2GRA-101 WASHINGTON 25, D.C., 19 April 1961

TM 11-2651, 1 November 1956, is changed as follows:Page 3. Add the following to paragraph 2c:

(3) Comments or suggestions. Any comments concerning omissions and discrepancies in appendix I and II will be prepared on DA Form 2028 and forwarded direct to Commanding Officer, U.S. Army Signal Materiel Support Agency. ATTN: SIGMS-ML, Fort Monmouth, N.J.

Page 58. Add the following appendixes:APPENDIX I

MAINTENANCE ALLOCATION CHARTFOR

ANTENNA GROUP AN/GRA-4Section I. INTRODUCTION

1. Generala. This section assigns maintenance functions and repair operations to be performed by the lowest appropriate

maintenance echelon.b. The columns are as follows:

(1) Part or component. This column shows only the nomenclature or standard item name. Additionaldescriptive data is included only where clarification is necessary to identify the part. Components andparts comprising a major end item are listed alphabetically. Assemblies and subassemblies are inalphabetical sequence with their components listed alphabetically immediately below the assembly listing.

*The changes supersede so much of Department of the Army supply manual SIG 7 & 8 AN/GRA-4, 25 September 1957,as pertains to first echelon items.

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(2) Maintenance function. This column indicates the various maintenance functions allocated to the echeloncapable of performing the operations.

(a) Service. To clean, to preserve, and to replenish fuel and lubricants.(b) Adjust. To regulate periodically to prevent malfunction.(e) Inspect . To verify serviceability and to detect incipient electrical or mechanical failure by scrutiny.(d) Test. To verify serviceability and to detect incipient electrical or mechanical failure by use of special

equipment such as gages, meters, etc.(e) Replace. To substitute service assemblies, subassemblies, and parts for unserviceable components.(f) Repair. To restore an item to serviceable condition through correction of a specific failure or

unserviceable condition. This function includes but is not limited to, inspecting, cleaning, preserving,adjusting, replacing, welding, riveting, and straightening.

(g) Aline. To adjust two or more components of an electrical system so that their functions are properlysynchronized.

(h) Calibrate. To determine, check, or rectify the graduation of an instrument, weapon, or weaponssystem, or components of a weapons system.

(i) Rebuild. To restore an item to a standard as near as possible to original or new condition inappearance, performance, and life expectancy. This is accomplished through the maintenancetechnique of complete disassembly of the item, inspection of all parts or components, repair orreplacement of worn or unserviceable elements using original manufacturing tolerances and/orspecifications and subsequent reassembly of the item.

(j) Overhaul. To restore an item to completely serviceable condition as prescribed by serviceabilitystandards developed and published by heads of technical services. This is accomplished throughemployment of the technique of Inspect and Repair Only as Necessary (IROAN). Maximumutilization of diagnostic and test equipment is combined with minimum disassembly of the itemduring the overhaul process.

(3) 1st, 2d, 3d, 4th, and 5th echelon. The symbol X indicates the echelon responsible for performing thatparticular maintenance operation, but does. not necessarily indicate that repair parts will be stocked at thatlevel. Echelons higher than the echelon marked by X are authorized to perform the indicated operation.

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(4) Tools required. This column indicates codes assigned to each individual tool equipment, test equipment,and maintenance equipment referenced. The grouping of codes in this column of the maintenanceallocation chart indicates the tool, test, and maintenance equipment required to perform the maintenancefunction.

(5) Remarks. Entries in this column will be utilized when necessary to clarify any of the data cited in thepreceding columns.

c. Columns in the allocation of tools for maintenance functions are as follows:

(1) Tools required for maintenance functions. This column lists tools, test, and maintenance equipmentrequired to perform the maintenance functions.

(2) 1st, 2d, 3d, 4th, and 5th echelon. The dagger (†) symbol indicates the echelons allocated the facility.(3) Tool code. This column lists the tool code assigned.

2. Mounting HardwareThe basic entries of the maintenance allocation chart do not include mounting hardware such as screws, nuts, bolts,

washers, brackets, clamps, etc.

3. Maintenance by Using OrganizationsWhen this equipment is used by signal services organizations organic to theater headquarters or communication

zones to provide theater communications, those maintenance functions allocated up to and including fourth echelon areauthorized to the organization operating this equipment.

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Section II. MAINTENANCE ALLOCATION CHART

Maintenance 1st 2nd 3rd 4th 5th ToolsParts or component function ech. ech. ech. ech. ech.required Remarks

(1) (2) (3) (4) (5) (6) (7) (8) (9)

ANTENNA GROUP AN/GRA-4 .......................... service X No facilities req'dinspect x 1

....................................................................... x 2test x 1, 3

X 2, 3replace xrepair X 2rebuild X

ANTENNA AS-244/GRA-4 ................................ replace XBAG ............................................................... replace XBLOCK, TACKLE ........................................... replace XBOX, CONNECTOR ...................................... replace XCABLE ........................................................... replace XCAP ............................................................... replace XCAPACITOR................................................... replace XCLAMP .......................................................... replace XCONNECTORS ............................................. replace XCOUPLING .................................................... replace XHANDLE ........................................................ replace XHOOK ............................................................ replace XINSULATORS................................................. replace XLAMP ............................................................. replace XLENS, INDICATOR LIGHT ............................ replace XLIGHT, INDICATOR........................................ replace X

4

Maintenance 1st 2nd 3rd 4th 5th ToolsParts or component function ech. ech. ech. ech. ech.required Remarks

(1) (2) (3) (4) (5) (6) (7) (8) (9)

PACKING PREFORMED . .............................. replace XPOST, BINDING ............................................ replace XREEL, WIRE .................................................. replace XROPE ............................................................ replace XSLEEVE.......................................................... replace XSLING, HOISTING ......................................... replace XSLING, CARRYING ....................................... replace XTAPE, MEASURING ...................................... replace XTOOL, ALIGNMENT ...................................... replace XTUNER, ANTENNA ........................................ replace X

rebuild XWASHER ....................................................... replace XWIRE ........................................................... . replace XMAST BASE AB-86/GRA-4 ............................ replace X Separate MAC.

REEL RL-122/GRA ........................................... replace X Separate MAC.

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Section IIl. AL.LOCATION OF TOOLS FOR MAINTENANCE FUNCTIONSTool required for maintenance functions 2d ech 3d ech 4th ech 5th ech Tool

(1) (3) (4) (5) (6) (7)

TOOL EQUIPMENT TE-41 (†) 1TOOL EQUIPMENT TE-113 (†) (†) (†) 2

2MULTIMETER TS-352/U (†) (†) (†) (†) 3

APPENDIX IIBASIC ISSUE ITEMS LIST FOR ANTENNA

GROUP AN/GRA-4Section I. INTRODUCTION

1. Scopea. This appendix lists items supplied for initial operation. The list includes tools, parts, and material issued as part

of the major end item. The list includes all items authorized for basic operator maintenance of the equipment. End itemsof equipment are issued on the basis of allowances prescribed in equipment authorization tables and other documentsthat are a basis for requisitioning.

b. Columns are as follows:(1) Source, maintenance, and recoverability code. Not used.(2) Federal stock number. This column lists the 11-digit Federal stock number.(3) Designation by model. Not used.(4) Description. Nomenclature or the standard item name and brief identifying data for each item are listed in

this column. When requisitioning, enter the nomenclature and description.(5) Unit of issue. The unit of issue is the supply term by which the individual item is counted for procurement,

storage, requisitioning, allowances, and issue purposes.(6) Expandability. Expendable items are indicated by the letter X; nonexpendable items are indicated by NX.(7) Quantity authorized. Under "Items Comprising an Operable Equipment", the column lists the quantity of

items supplied for the initial operation of the equipment.(8) Illustration. Not used.

2. ReferencesAdditional instructions concerning maintenance of this equipment are contained in TM 11-5895-229-12P, (Operator andOrganizational Maintenance Repair Parts and Special Tool Lists and Maintenance Allocation Chart: Mast AB-86/GRA-4.

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Section II. FUNCTIONAL PARTS LIST

Federal stock No. Description Unit of Expand- Quan-issue ability tity author

ized(2) (4) (5) (6) (7)

ITEMS COMPRISING ANOPERABLE EQUIPMENTANTENNA GROUP AN/GRA-4

5820-244-5147 ANTENNA GROUP AN/GRA-4: pro- ea NXvides several ant types for freq of 1.5to 18.0 mc; J and H Smith part/dwgNo. 100.

Ord thru AGC TECHNICAL MANUAL: TM 11-2651 ea X 25820-264-7506 ANTENNA AS-244/GRA-4: 1.5 to 18.0 ea NX 1

mc freq range; wire construction, forreceiver and transmitter signals.ANTENNA AS-244/GRA-4

5820-497-9628 BAG, BG-102, BG-102A, C ea X 15995-247-9759 CORD CG-357/U: (50 ft 6 in) uses RG- ea X 6

59A/U cable; SigC dwg No. SC-D-34932.

5970-405-8223 INSULATOR IL-4/GRA-4: with RF ea X 1Receptacle UG-58/U.

6240-223-9100 LAMP, GLOW: 105-120 V, 1/25 w, 0.003 ea X 1amp; miniature bayonet base, 1/8 in.max o/a, h; GE type No. NE-51.

5985-497-8765 REEL RL-122/GRA-4 ea NX 25985-228-8064 SLING, HOISTING: Halyard MX-516/ ea X 1

GR-A.5210-265-7451 TAPE, MEASURING: 100 ft Ig ex- ea NX 1

tended; Justus Roe Model No. 400-A1.5120-408-1701 TOOL, ALINEMENT: approx. 5/32 in. x ea X 1

1/32 in. thk sedr nib in one end, 6 in. lg x7/32 in. dia; Amer Rad Hdwe No. 860.

5985-355-8024 TUNER, ANTENNA: Antenna Tuner ea X 1TN-174/GRA-4.

5985-257-2927 MAST AB-86/GRA-4: sectionalized ea NX 1construction; J and H Smith part No.100-B.

RUNNING SPARES ANDACCESSORY ITEMS

ANTENNA GROUP AN/GRA-4NO PARTS AUTHORIZED FOR

STOCKAGE AT FIRST ECHELON

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By Order of the Secretaries of the Army and the Air Force:

G. H. DECKER,General, United States Army,

Official: Chief of Staff.R. V. LEE,

Major General, United States Army,The Adjutant General.

CURTIS E. LeMAY,Official: Chief of Staff, United States Air Force.

R. J. PUGH,Colonel, United States Air Force,Director of Administrative Service.

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Distribution:Active Army: To be distributed in accordance with DA Form 12-7 requirements for TM 11-series (Unclas) plus the

following:USASA (2) 11-16CNGB (1) 11-55Tech Stf, DA (1) except 11-57

CsigO (18) 11-96DASA (5) 11-97ARADCOM (2) 11-98ARADCOM Rgn (2) 11-117MDW (2) 11-500 (AA-AE, RA-RT) (4)Seventh USA (2) 11-555EUSA (2) 11-557Corps (2) 11-587Div (2) 11-592Units organized under following 11-597

TOE's (2 copies to each 17-51unless otherwise indicated): 29-56

1-7 30-151-17 30-221-37 30-500 (AA-AK)1-67 32-571-107 39-615-15 44-355-16 44-365-17 44-2355-237 44-2365-278 44-2377-52 44-4358-76 44-4368-78 44-4378-137 44-4459-47 44-4469-65 44-4479-75 44-4489-87 44-5359-117 44-5369-227 44-5379-500 (AA-AC) 44-5449-510 (AA-AC) 44-54510-22 44-54610-202 44-54710-206 44-54810-377 55-1110-445 55-1210-448 55-1610-536 55-5611-5 55-5711-7 55-116NG: None.USAR: None.For explanation of abbreviation used, see AR 320-50.

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Changes now in force: C 1, C 2TM 11-2651

C2

ANTENNA GROUPS AN/GRA-4 AND AN/GRA-12

CHANGE HEADQUARTERSDEPARTMENT OF THE ARMY

No. 2 WASHINGTON D. C., 16 October 1963

TM 11-2651, 1 November 1966, is changed as follows:

Note. The parenthetical references to a previous change (example "page 1 of C1") indicates that pertinent materialwas published in that change.

Page 3. Delete paragraph 1 and substitute:

1. ScopeThis manual describes Antenna Groups AN/GRA- and AN/ GRA-12 and covers their installation, operation,

theory, operator's maintenance, and second echelon maintenance. It also includes instructions for performing preventiveand periodic maintenance services and repair functions to be accomplished by the organizational repairman.

Add paragraph 1.1 after paragraph 1.

1.1. Index of PublicationsRefer to the latest issue of DA Pam 310-4 to determine whether there are new editions, changes, or additionalpublications pertaining to the equipment. DA Pam 310-4 is an index of current technical manuals, technical bulletins,supply bulletins, lubrication orders, and modification work orders available through publications supply channels. Theindex lists the individual parts (-10, -20, -35P, etc.) and the latest changes to and revisions of each equipmentpublication.

Delete paragraph 2 (page 1 of C1) and substitute:

2. Forms and Recordsa. Reports of Maintenance and Unsatisfactory Equipment. Use equipment forms and records in accordance with

instructions in TM 38-750.b. Report of Damaged or Improper Shipment. Fill out and forward DD Form 6 (Report of Damaged or Improper

Shipment) "s prescribed in AR 700-58 (Army), NAVSANDA Publication 378 (Navy), and AFR 71-4 (Air Force).

TAGO 6513B

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c. Reporting of Equipment Manual Improvements. The direct reporting by the individual user of errors, omissions,and recommendations for improving this manual is authorized and encouraged. DA Form 2028 (Recommended changesto DA technical manual parts lists or supply manual 7, 8, or 9) will be used for reporting these improvements. This formwill be completed in triplicate using pencil, pen, or typewriter. The original and one copy will be forwarded direct to:Commanding Officer, U.S. Army Electronics Materiel Support Agency, ATTN: SELMS-MP, Fort Monmouth, New Jersey07703. One information copy will be furnished to the individual's immediate supervisor (e.g., officer, noncommissionedofficer, supervisor, etc.).

Page 5, paragraph 5b: Delete note 2 and substitute:

2. This listing is based on the original shipment by the contractor. For the current official listing of components ofindividual models, see the basic issue items list (app. III).

Page 23. Delete paragraph 14d and substitute:

d. Checking Unpacked Equipment.

(1) Inspect the equipment for damage incurred during shipment. If the equipment has been damaged, reportthe damage on DD Form 6 (par. 2).

(2) Check the equipment against the master packing list. When no packing list accompanies the equipment,check the equipment against the table of components in paragraph 5. Report all discrepancies inaccordance with instructions in TM 38-750 (par. 2).

NoteShortage of a minor assembly or part that does not effect proper functioning of the equipmentshould not prevent use of the equipment.

(3) If the equipment has been used or reconditioned, see whether it has been changed by a Modification WorkOrder (MWO). The current MWO's applicable to the equipment are listed in DA Pam 310-4 (par. 1.1).

Page 27. Make the following changes:

Paragraph 16f. Add subparagraph g after subparagraph f.

g. After the mast has been raised, bring the guys to the correct tension. Tension must be applied at a uniform rateto prevent twisting the mast. To adjust guy tension, tighten two guys simultaneously, first on one side of the mast andthen on the other side of the mast. Increase the tension gradually and evenly until the guys are brought under propertension.

AGO 6513B

2

Page 40, chapter 3. Heading. Change the chapter heading to read:

CHAPTER 3

MAINTENANCE INSTRUCTIONS

Delete the note immediately after the chapter heading.Delete paragraphs 21 through 24 and substitute:

21. Scope of Maintenance

The maintenance duties assigned to the operator of the equipment are listed below together with a reference to theparagraphs covering the specific maintenance functions. These procedures do not require special tools or testequipment.

a. Daily preventive maintenance checks and services (par. 24).b. Cleaning (par. 24.1).c. Replacement of defective pilot lamp (par. 30).

22. Preventive Maintenance

Preventive maintenance is the systematic care, servicing, and inspection of equipment to prevent the occurrenceof trouble, to reduce downtime, and to assure that the equipment is serviceable.

a. Systematic Care. The procedures given in paragraphs 24 and 24.1 cover routine systematic care and cleaningessential to proper upkeep and operation of the equipment.

b. Preventive Maintenance Checks and Services. The preventive maintenance checks and services chart (par.24.1) outlines functions to be performed at specific intervals. These checks and services are to maintain Army electronicequipment in a combat serviceable condition; that is, in good general (physical) condition and in good operatingcondition. To assist operators in maintaining combat serviceability, the chart indicates what to check, how to check, andwhat the normal conditions are; the References column lists the illustrations, paragraphs, or manuals that containsupplementary information. If the defect cannot be remedied by the operator, higher echelon maintenance or repair isrequired. Records and reports of these checks and services must be made in accordance with the requirements set forthin TM 38-750.

23. Preventive Maintenance Checks and Services Periods

Preventive maintenance checks and services of the equipment are required daily. Paragraph 24 specifies thechecks and services that must be accomplished daily and under the conditions listed below.

AGO 65133

a. When the equipment is initially installed.b. When the equipment is reinstalled after removal for any reason.c. At ]east once each week if the equipment is maintained in standby condition.

24. Daily Preventive Maintenance Checks and Services Chart

SequenceNo. Item Procedure Reference

1 Connections Check to be sure that all cable con- Fig. 17nections are secure and properly throughtightened. 22 and 24

2 Cables Check to be sure that all cables Fig. 24.show no evidence of damage ordeformity. Inspect the cable forcuts, kinks, or damaged insula-tion.

3 TN-174/GRA-4 Warning: Do not make any replace- Fig. 23.ments or adjustment on theequipment with power on.

Adjust the tuning control and ob-serve that the neon bulb glowswith varying intensity. Replacea defective neon bulb.

Add paragraph 24.1 after paragraph 24:

24.1. Cleaning

Inspect the exterior of the equipment. The exterior surfaces should be clean, and free of dust, dirt, grease, andfungus.

a. Remove dust and loose dirt with a clean soft cloth.

Warning: Cleaning compound is flammable and its fumes are toxic. Provide adequateventilation. Do not use near a flame.

b. Remove grease, fungus, and ground-in dirt from the mast assembly of the AN/FRA4 and AN/FRA-12; use a clothdampened (not wet) with cleaning compound (Federal stock No. 7930-395-9542).

Page 41. Delete figure 27.

Page 42. section II. Heading. Change the section heading to read:

Section II. ORGANIZATIONAL MAINTENANCE

AGO 6513B

4

Delete paragraphs 25 through 28 and substitute:

25. Scope of Organizational Maintenance

a. This section contains instructions covering second echelon maintenance of the equipment. It includesinstructions for performing preventive and periodic maintenance services and repair functions to be accomplished by theorganizational repairman.

b. Second echelon maintenance of the equipment includes:

(1) Preventive maintenance (par. 28 and 28.1).(2) Touchup painting instructions (par. 28.2).(3) Troubleshooting (par. 29).(4) Replacement of parts (par. 30).

26. Tools, Materials, and Test Equipment Required

The tools and test equipment required for operational maintenance are listed in the maintenance allocation chart(app. I). The materials required are as follows:

a. Cleaning Compound (Federal stock No. 7930-39-9542).b. Cleaning cloth.

27. Organizational Preventive Maintenance

a. Preventive maintenance is the systematic care, inspection, and servicing of equipment to maintain it inserviceable condition, prevent breakdowns, and assure maximum operational capability. Preventive maintenance is theresponsibility of all echelons concerned with the equipment and includes the inspection, testing, and repair orreplacement of parts, subassemblies, or units that inspection and tests indicate would probably fail before the nextscheduled periodic service. Preventive maintenance checks and services of the equipment at the second echelon levelare made at monthly and quarterly intervals unless otherwise directed by the commanding officer.

b. Maintenance forms and records to be used and maintained on this equipment are specified in TM 38-750.

28. Monthly Maintenance

Perform the maintenance functions indicated in the monthly preventive maintenance checks and services chart(par. 28.1). A month is defined as approximately 30 calendar days or 8-hour-perday operation. If the equipment isoperated 16 hours a day, the monthly preventive maintenance checks and services should be performed at 15-dayintervals. Adjustment of the maintenance interval must be made to compensate for any unusual operating conditions.Equipment maintained in a standby (ready for immediate operation) condition must have monthly preventivemaintenance checks and services performed on it. Equipment in limited storage (requires service before operation) doesnot require monthly preventive maintenance.

AGO 6513B

5

Add paragraphs 28.1 and 28.2 after paragraph 28:

28.1. Monthly Preventive Maintenance Checks and Services Chart

SequenceNo. Item Procedure Reference

1 Publications Check to see that the technical DA Pammanual is complete and in usable 310-4.condition. Check DA Pam 310-4to determine if new, applicablechanges have been published.

2 Modification work Check to see that all URGENT DA Pamorders. MWO's have been applied to the 310-4.

equipment and that all NOR-MAL MWO's have been scheduled.

8 Ground rod Check to see that the ground rodsare firmly embedded in the soiland that the grounding wire isfirmly attached to them.

4 Mast Check to see that the mast is level.If the mast is badly distortedand cannot be leveled because ithas settled unevenly, dismantlethe mast and reassemble it on afirmer foundation.

5 Guys Check for badly rusted or frayedguys. See that the guys are se-curely attached to the mast.Check and adjust the tension onthe guys.

28.2. Touchup Painting Instructions

Clean rust and corrosion from metal surfaces by lightly sanding them with fine sandpaper. Brush two thin coats of painton the bare metal to protect it from further corrosion. Refer to the applicable cleaning and refinishing practices specifiedin TM 9-213.

Page 43. Delete figure 28.

AGO 6513B

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Page 58, appendix I (page 1 of C 1). Change "appendix I" to: appendix II.Add appendix I before II:

APPENDIX IREFERENCES

The following is a list of references applicable and available to the operator and organizational repairman of AntennaGroups AN/GRA-4 and AN/GRA-12:

DA Pam 310-4 Index of Technical Manuals, Technical Bulletins, Supply Bulletins, Lubrication Orders, and Modification Work Orders.

SIG 7&8 AN/GRA-12 Antenna Group AN/GRA-12.SIG 7&8 RL-122/GRA-4 Reel RL122/GRA4.TM 9-213 Painting Instructions for Field Use.TM 11-5895-229-12P Operator and Organizational Maintenance Repair Parts and Special Tools List and

Maintenance Allocation Chart: AB-86/GRA-4.TM 11-5985-231-20P Organizational Maintenance Repair Parts and Special Tools List: Antenna Group

AN/GRA-4.TM 38-750 The Army Equipment Record System and Procedures.

Appendix II (page 6 of C 1). Change "appendix II" to appendix III.Section I. Delete paragraph 2, "references".Section II (page 7 of C 1). Make the following changes:Add the following item in the columns indicated below:

2 4 5 6 7

5985-257-2927

ITEMS COMPRISING ANOPERABLE EQUIPMENT

ANTENNA GROUP AN/GRA-4MAST AB-86/GRA-4: sectionalized 2

construction; J and H Smith partNo. 100B.

ea NX 2

"ANTENNA AS-244/GRA-4". Make the following changes:Column 2, "5985-497-8765". Column 7, change "2" to: 3Column 2, "5985-228-8064". Column 7, change "1" to: 2Column 2, "5985-257-2927". Delete item in its entirety.

AGO 6513B

7

By Order of the Secretary of the Army:EARLE C. WHEELER,General, United States Army.

Official: Chief of Staff.J. C. LAMBERT,Major General, United States Army.The Adjutant General.

Distribution:To be distributed in accordance with DA Form 12-32, Sec II (Unclas) requirements for Nike Hercules andImproved Nike Hercules and Target Missiles and Pershing and Nike Ajax and Hawk, TM, Radio.

AGO 3613B

8

Changes in force: C 1, C 2, and C 3TM 11-2651

C3CHANGE HEADQUARTERS

DEPARTMENT OF THE ARMYNo. 3 WASHINGTON, D.C., 31 October 1973

ANTENNA GROUPS AN/GRA-4AND AN/GRA-12

TM 11-2651/TO31R2-2GRA-101, 1 November 1956, is changed as follows:

Page 3, paragraph 1.1. Delete paragraph 1.1 and substitute new paragraph 1.1.

1.1. Indexes of Publications

a. DA Pam 310-4. Refer to the latest issue of DA Pam 310-4 to determine whether there are new editions,changes, or additional publications pertaining to the equipment.

b. DA Pam 310-7. Refer to DA Pam 310-7 to determine whether there are modification work orders (MWO's)pertaining to the equipment.

Paragraph 2. Delete paragraph 2 and substitute new paragraph 2.

2. Forms and Records

a. Reports of Maintenance and Unsatisfactory Equipment. Maintenance forms, records, and reports which are to beused by maintenance personnel at all maintenance levels are listed in and prescribed by TM 38-750.

b. Report of Packaging and Handling Deficiencies. Fill out and forward DD Form 6 (Report of Packaging andHandling Deficiencies) as prescribed in AR 700-58 (Army)/NAVSUP PUB 378 (Navy)/AFR 71-4 (Air Force)land MCOP4030.29 (Marine Corps).

c. Discrepancy in Shipment Report (DISREP) (SF 361). Fill out and forward Discrepancy in Shipment Report(DISREP) (SF 361) as prescribed in AR 55-38 (Army)/NAVSUP PUB 459 (Navy)/AFM 75-34 (Air Force)/and MCOP4610.19 (Marine Corps).

Add paragraph 2.1 after paragraph 2.

TAGO 3169B

}

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2.1. Reporting of Equipment Publication Improvements

The reporting of errors, omissions. and recommendations for improving this publication by the individual user isencouraged. Reports should be submitted on DA Form 2028 (Recommended Changes to Publications) and forwardeddirect to Commander, US Army Electronics Command, ATTN: AMSELMA-C, Fort Monmouth, NJ 07703.

Page 5. After paragraph 4 add paragraph 4.1.

4.1. Items Comprising an Operable Antenna Group AN/GRA-4 (FSN 5820-244-5147).

FSN QTY Nomenclature, part No., and mfr code

NOTEThe part number is followed by the applicable5-digit Federal supply code for manufacturers(FSCM) identified in SB 708-42 and used toidentify manufacturer, distributor, orGovernment agency, etc.

5820-264-7506 1 Antenna AS-244/GRA-4: 1.5 to18.0 mHz freq range, wire con-struction, for receiver andtransmitter signals.

5996-247-9759 6 Cord CG-357/U: (50 ft 6 in.)user RG-59A/U cable; SC-D-34932, 80063

5970-405-8223 1 Insulator IL-4/GRA-4: with RFreceptable UG-58/U

5985-497-8765 3 Reel RL-122/GRA-4, SC-D-34897,80063

5210-265-7451 1 Tape, Measuring: 100 ft lgextended, 400-A1, 86794

5985-355-8024 1 Tuner, Antenna: antenna tunerTN-174/GRA-4, SC-D-34917, 80063

5985-257-2927 2 Mast AB-86/GRA-4: sectionalizedconstruction, 100B, 82241

2

Page 58, appendix III.

Delete appendix III and substitute new appendix III.

APPENDIX III

BASIC ISSUE ITEMS LIST AND ITEMS TROOPINSTALLED OR AUTHORIZED LIST

Section I. INTRODUCTION

1. Scope.

This appendix lists basic issue items and items troop installed or authorized required by the crew/operator for installation,operation, and maintenance of Antenna Group AN/GRA-4.

2. General.

This Basic Issue Items and Items Troop Installed or Authorized List is divided into the following sections:

a. Basic Issue Items List-Section II. A list, in alphabetical sequence, of items which are furnished with, and whichmust be turned in with the end item.

b. Items Troop Installed or Authorized List-Section llI. A list, in alphabetical sequence, of items which, at thediscretion of the unit commander, may accompany the end item, but are not subject to be turned in with the end item.

3. Explanation of Columns.

The following provides an explanation of columns found in the tabular listings:

a. Illustration. Not applicable.b. Federal Stock Number. Indicates the Federal stock number assigned to the item and will be used for

requisitioning purposes.c. Part Number. Indicates the primary number used by the manufacturer (individual, company, firm. corporation,

or Government activity), which controls the design and characteristics of the item by means of its engineering drawings,specifications standards, and inspection requirements, to identify an item or range of items.

d. Federal Supply Code for Manufacturer (FSCM). The FSCM is a 5-digit numeric code used to identify themanufacturer, distributor, or Government agency, etc., and is identified in SB 708-42.

3

e. Description. Indicates the Federal item name and a minimum description required to identify the item.

f. Unit of Measure (U/M). Indicates the standard of basic quantity of the listed item as used in performing theactual maintenance function. This measure is expressed by a two character alphabetical abbreviation, (e.g., ea, in., pr,etc.). When the unit of measure differs from the unit of issue, the lowest unit of issue that will satisfy the required units ofmeasure will be requisitioned.

g. Quantity Furnished with Equipment (Basic Issue Items Only). Indicates the quantity of the basic issue itemfurnished with the equipment.

h. Quantity Authorized (Items Troop Installed or Authorized Only). Indicates the quantity of the item authorized tobe used with the equipment.

Section II. BASIC ISSUE ITEMS LIST

(1) (2) (3) (4) (5) (6) (7)Illustration Federal Unit Qty

Stock Part of Furn(A) (B) Number Number FSCM Description Meas With

equipFig. Item UsableNo. No. on

Code

5830-497-9628 71-3308 80063 BAG, BG-102, EA 1BG-102A

5985-228-8064 SC-C-28054 80063 SLING, HOISTING: EA 2HALYARDMX-516/GR-A

Section III. ITEMS TROOP INSTALLED OR AUTHORIZED LIST

(1) (2) (3) (4) (5) (6)Federal Part FSCM Description Unit QtyStock Number Usable of AuthNumber on Code Meas

5120-288-7783 860 83330 TOOL ALIGNMENT: EA 1APPROX 5/32 in. X1/32 in. THK, SEDRNIB IN ONE END,6 in. LG X 7/32 IN.DIA

4

By Order of the Secretary of the Army:CREIGHTON W. ABRAMSGeneral, United States ArmyChief of Staff

Official:

VERNE L. BOWERSMajor General, United States ArmyThe Adjutant General

Distribution:To be distributed in accordance with DA Form 12-51 operator maintenance requirements for AN/GRA-4 and

AN/GRA-12.

*TM 11-2651

TECHNICAL MANUAL DEPARTMENT OF THE ARMYNo. 11-2651 WASHINGTON 25, D. C., 1 November, 1956

ANTENNA GROUPS AN/GRA-4 AND AN/GRA-12

Paragraph PageCHAPTER 1. INTRODUCTION

SECTION I. General.Scope ................................................................................... 1 3Forms and records ................................................................ 2 3

II. Description and data.Purpose and use ................................................................... 3 5Technical characteristics ....................................................... 4 6Components ......................................................................... 5 5Common name and nomenclature ........................................ 6 10Description of Antenna Mast Assembly

AB-86/GRA-4 . ................................................................. . 7 11Description of Antenna AS-244/GRA-4 .................................. 8 12Description of Accessory Kit MX-1137/GRA-12...................... 9 13Running spares ..................................................................... 10 13Differences between Antenna Groups

AN/GRA-4 and AN/GRA-12 ............................................. . 11 14CHAPTER 2. INSTALLATION

Selecting type of antenna ..................................................... 12 15Siting .................................................................................. . 13 17Unpacking ............................................................................. 14 20Installation of mast assembly ............................................... . 15 23Raising mast ......................................................................... 16 26Determining length of antenna .............................................. 17 27Installing antenna, using Antenna Group

AN/GRA-4 ........................................................................ 18 30Installing antenna, using Antenna Group

AN/GRA-12 ...................................................................... 19 38Tuner TN-174/GRA-4, control ............................................... 20 39

3. ORGANIZATIONAL MAINTENANCESECTION I. First echelon (operator) maintenance.

Scope of operator's maintenance .......................................... 21 40Tools, materials, and test equipment required ....................... 22 40Operator's preventive maintenance ....................................... 23 40Visual inspection ................................................................... 24 41

II. Second echelon (unit repairman) maintenance.Scope of unit repairman's maintenance ................................ 25 42Tools, materials, and test equipment required........................ 26 42Unit repairman's preventive maintenance . ............................ 27 42Unit repairman's visual inspection ......................................... 28 42Troubleshooting .................................................................... 29 44Replacement of parts ............................................................ 30 45

CHAPTER 4. THEORYCircuit theory ........................................................................ 31 48Antenna circuits .................................................................... 32 50Tuner TN-174/GRA-4 ............................................................ 33 54

5. SHIPMENT, LIMITED STORAGE, ANDDEMOLITION

SECTION I. Shipment and limited storage.Disassembly of equipment .................................................... 34 56Repacking for shipment or limited storage ............................ 35 57

II. Demolition of material.Authority for demolition.......................................................... 36 58Methods of destruction .......................................................... 37 58

*This manual supersedes TM 11-2651, 21 July 1952

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}

1

Figure 1. Antenna Group AN/GRA-4.

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CHAPTER 1

INTRODUCTION

Section I. GENERAL

1. Scope

a. This manual contains information for the installation, operation, maintenance, and repair of Antenna GroupAN/GRA-4 (fig.1) and Antenna Group AN/GRA-12 (fig. 2).

b. Forward comments on this publication directly to Commanding Officer, The Signal Corps Publications Agency,Fort Monmouth, N. J.

2. Forms and Records

a. Unsatisfactory Equipment Reports. Fill out and forward DA Form 468 (Unsatisfactory Equipment Report) toCommanding Officer, Signal Equipment Support Agency, Fort Monmouth, N. J., as prescribed in AR 700-38.

b. Damaged or Improper Shipment Report. Fill out and forward DD Form 6 (Report of Damaged or ImproperShipment) as prescribed in AR 700-58 (Army); Navy Shipping Guide, Article 1850-4 (Navy); and AFR 71-4 (Air Force).

c. Preventive Maintenance Forms.

(1) DA Form 11-238 (Operator First Echelon Maintenance Checklist for Signal Corps Equipment (RadioCommunication, Direction Finding, Carrier, Radar)) will be prepared in accordance with instructions on theback of the form (fig. 27).

(2) DA Form 11-239 (Second and Third Echelon Maintenance Checklist for Signal Corps Equipment (RadioCommunication, Direction Finding, Carrier, Radar)) will be prepared in accordance with instructions on theback of the form (fig. 28).

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Figure 2. Antenna Group AN/GRA-12.

4

Section II. DESCRIPTION AND DATA

3. Purpose and Use

Antenna Groups AN/GRA-4 and AN/GRA-12 are portable, half-wave antenna assemblies designed for the transmission and reception of radio signalsbetween 1.5 and 18 megacycles (mc).

a. The AN/GRA-4 antenna is used in conjunction with any radio set that has a transmitter output of less than 100 watts and a characteristic impedance of 72or 500 ohms. Several different types of antennas can be set up by using various combinations of the components supplied.

b. The AN/GRA-12 antenna is used with any radio set having a transmitter output of 500 watts or less and has a characteristic impedance of 52 ohms.

4. Technical Characteristics

a. Antenna Group AN/GRA-4.

Power input ................................ ................................ ......................... Up to 100 watts.Frequency range................................ ................................ .................. 1.5 to 18 mc.Weight ................................ ................................ ................................ . 169 pounds.Antenna type................................ ................................ ........................ Half-wave.Impedance................................ ................................ ........................... 72 or 500 ohms.

b. Antenna Group AN/GRA-12

Power input ................................ ................................ ......................... Up to 500 watts.Frequency range ................................ ................................ ................. 1.5 to 18 mc.Weight ................................ ................................ ................................ 229 poundsAntenna type................................ ................................ ........................ Center-fed Hertz (half-wave).Impedance................................ ................................ ........................... 52 ohms.

5. Components

a. Antenna Group AN/GRA-4 consists of one Antenna AS244/GRA-4 and two Antenna Mast Assembly AB-86/GRA-4 (fig. 1). The antenna includeswire, insulators, halyards, tuning unit, and a carrying case. The mast assembly consists of 16 metal mast sections, a whip adapter, counterpoise, halyard,insulator, associated guys and stakes, and a carrying case. The units may be used to construct several different antenna combinations.

b. Antenna Group AN/GRA-12 consists of one Accessory Kit MX-1137/GRA-.12 and three Antenna Mast Assembly AB86/GRA-4 (fig. 2). The accessory kitincludes wire, a cable assembly, measuring tape, and carrying case. Each mast assembly contains 16 metal mast sections, a whip adapter, a counterpoise, ahalyard, an insulator, associated guys and stakes, and a carrying case. The antenna group is used to construct a center-fed Hertz antenna.

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Unit weightRequired

Component No. Height (in.) Depth (in.) Length (in.) (lb) (Oz)

Antenna Mast Assembly AB-86/GRA-4 5 10 1/2 8½ 36 69 7Mast Section AB-85/GRA-4 16 3 (ft) 1.625 OD 2 8Frame MX-1116/GRA-4 1 8% 10 1/2 35Hammer HM-1 1 2 9Counterpoise CP-12 1 25 (ft) 1 11

eachradial

Insulator MX-384/GRA-4 1 16 9/16 2 13/16 dia 2 15Mast Base AB-154/U 1 17 1/2 13/8 dia 12Wire W-128 1 10 (ft) 9Guy Stake GP-111/G 4 18 1 1/4 1 1/4 1Guy MX-383/GRA-4 4 3/16 dia 50 (ft) 12Guy MX-381/GRA-4 4 3/16 dia 40 (ft) 11Guy MX-382/GRA-4 4 3/16 dia 31 (ft) 10Guy Plate MX-378/U 3 .089 thk 3 dia 2Antenna Adapter MX-857/GRA-4 1 9 1 5/8 dia 13Halyard MX-516/GRA-4 1 3/16 dia 140 (ft) 2

Antenna AS-244/GRA-4 1 14 9 14 29 8Bag BG-102-A 1 14 5 14 2 13Reel RI122/GRA-4 3 2 4.25 12.5 2 3Cord CG-357/U 6 50 (ft) 1 15Insulator IL-4/GRA-4 1 3.5 3 1 8Tape, stainless steel (100 ft) 1 .5 4.5 4.5 1 3Halyard MX-516/GRA-4 2 3/16 dia 140 (ft) 2Lead-in Wire W-128 2 10 (ft) 9o Tuner TN-174/GRA-4 1 4 3 6 ½ 1 11

Accessory Kit MX-1137/GRA-12 1 20 2Bag CW-206/GR 1 11 3 11 1/2 2 13

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Reel Assembly RL122/GRA-4 3 2 4.25 12.5 2 3Tape, stainless steel (100 ft) 1 5 4.5 4.5 1 3RF Cable Assembly CG-692/U 1 75 (ft) 9 1Hook assembly 2 1.25 1.25 7.0 4

Notes:1. Refer also to paragraph 10.2. This list is for general information only. See appropriate supply publications for information pertaining to requisition of spare parts.3. Antenna Group AN/GRA-12 requires three Masts AB-86/GRA-4.

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Figure 3. Antenna Mast Assembly AB-86/GRA-4, components.

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Figure 4. Antenna AS-244/GRA-4, components.%o

Figure 5. Accessory Kit MX-1137/GRA-12, components.

6. Common Name and Nomenclature

A list of the nomenclature assignments for the components of Antenna Groups AN/GRA-4 and AN/GRA-12 is givenbelow. A common name is indicated after each item.

Nomenclature Common name

Antenna Mast Assembly Antenna mast assembly or mastAB-86/GRA-4 assembly

Mast Section AB-85/GRA-4 Mast sectionFrame MX-1116/GRA-4 FrameCounterpoise CP-12 CounterpoiseMast Base AB-154/U Mast baseHalyard MX-516/GRA-4 HalyardInsulator MX-384/GRA-4 InsulatorAntenna AS-244/GRA-4 Antenna or antenna assemblyReel RL-122/GRA-4 Reel assemblyTuner TN-174/GRA-4 TunerAccessory Kit MX-1137/GRA-12 Accessory kitGuy Stake GP-111/G Guy stakeAntenna Adapter MX-857/GRA-4 Antenna adapterGuy Plate MX-378/U Guy plateGuy MX-381/GRA-4 40 ft guyGuy MX-382/GRA-4 31 ft guyGuy MX-383/GRA-4 50 ft guy

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7. Description of Antenna Mast Assembly AB-86/GRA-4(fig. 3)

a. Mast Section AB-85/GRA-4 is a 3-foot aluminum tube. One end of the tube is smaller in diameter so that it canbe fitted into the larger end of the next section, thus reducing the effective length of each section to 21/2 feet. A set ofcontact fingers is mounted in the larger end of each section to assure positive contact between sections when the mast isused as a vertical antenna.

b. Frame MX-1116/GRA-4 consists of two aluminum end plates. Each of these plates has 11 tube fittings which fitinto the mast sections. When assembled with the mast sections for transportation, the end plates are held in place by asteel cable. A turnbuckle keeps the cable taut. Eleven of the mast sections form a trough in which two mast sectionsand all the other components of the mast assembly can be packed. The other three mast sections fit into a rack and arestrapped into place, thus serving as the top of the case. A handle is provided at each end for carrying.

c. Counterpoise CP-12 (fig. 16) consists of a center plate, four 25-foot radials, and a ground wire. It is used for aground system when the mast is used as a 40-foot or 55-foot vertical radiator.

d. Insulator MX-384/GRA-4 is a molded fiberglass insulator. It fits at the junction of any two mast sections butnormally is used at the mast base.

e. Antenna Adapter MX-857/GRA-4 is a 9-inch aluminum tube fitted on one end with a set of contact fingers to fitover the top mast section. The other end forms a receptacle for additional mast sections to permit extending the over-allmast to 55 feet for special uses. Three Mast Sections MS-116, one Mast Section MS-117, and one Mast Section MS-118are required with the adapter for this service. These mast sections are not furnished with Antenna Group AN/GRA-4 andmust be requisitioned.

f. Mast Base AB-154/U (swivel stake) consists of an aluminum stake with a pivoting clevis at one end. The upperportion of the clevis fits into the lower end of a mast section or the base insulator.

g. The lead-in wire is a 10-foot section of Wire W-128. It serves as the transmission line between the antenna andthe tuning unit.

h. Guy Stake GP-111/G is constructed of metal and is 18 inches long. A fastener which is permanently attached tothe top of the stake fastens to the guys.

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i. Guys MX-383/GRA-4, MX-381/GRA-4, and MX382/GRA-4 are all similar, the only differences being in the colorcode (red, white, and blue, respectively) and the length (50 feet, 40 feet, .and 31 feet, respectively). They are made of3/16-inch, three-strand twist rope. One end is provided with a length-adjustment Fastener FT-9; a snap hook and straininsulator are attached to the other end.

j. Guy Plate MX-378/U consists of a round steel plate 3 inches in diameter. The center hole fits over the male endof a mast section, and five outer holes serve for attaching the four guy ropes and a halyard.

k. Halyard MX-516/GRA-4 consists of a 140-fqot length of 3/16-inch, three-strand twist rope. One end of the rope isfitted with an insulator and a fastener which attaches to Reel RL122/GRA-4 or directly to Wire W-120. A pulley whichfloats on the halyard attaches to the top guy plate with a snap hook.

8. Description of Antenna AS244/GRA-4(fig. 4)

a. Bag BG-102-A is constructed of heavy canvas and is used for storage of small components.

b. Reel Assembly RL-122/GRA- consists of one Reel RL 122/GRA-4 and 150 feet of Wire W-120. Each end of thewire is equipped with a mating termination so that the wires from any number of reels can be combined to make uplonger antennas. Two small holes are provided in the reel handle for connection to the halyard.

c. Cord CG-357/U consists of 50 feet of Radio Frequency Cable RG-59A/U which has an impedance of 72 ohms.The cable is terminated with a male and female coaxial fitting in either end. It is used with the center-fed Hertz (doublet)antenna installation (fig. 10).

d. Insulator IL-4/GRA-4 consists of laminated phenolic plates, having two terminals for connection of Wire W-120(antenna wire) and a female coaxial fitting for connection of Cord CG357/U. The insulator is used at the center of thedoublet. antenna installation.

e. The stainless steel measuring tape is 100 feet long. It is used to measure the length of antenna necessary foroperation at a given frequency.

f. Halyard MX-516/GRA-4 consists of 140 feet of nylon rope, 3/16 inch in diameter. An insulator and fastener areattached to one end of the rope. The fastener can be connected to the reel or directly to Wire W-120. A pulley floats onthe halyard and is attached to the top guy plate by means of a snap hook.

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g. The lead-in wire is a 10-foot section of Wire W-128. In use, one end of the wire is connected to Wire W-120(antenna reel), and the other end is connected to the tuning unit.

h. Antenna Tuner TN-174/GRA-4 consists of a 12- to 244micromicrofarad (sef) variable capacitor. A neon bulb iswired in parallel to indicate resonance during antenna loading, and a slotted shaft adjustment is provided to vary thecapacitance. Two wires are permanently connected to the unit; one wire is fitted with a wire termination which attachesto the antenna lead-in wire, and the other wire connects directly to the radio set. A binding post for a ground connectionis also provided.

9. Description of Accessory Kit MX-1137/GRA-12(fig. 5)

a. Bag CW-206/GR is constructed of heavy canvas and serves as a storage case for the other components of thekit.

b. Reel Assembly RT-122/GRA-4 consists of one Reel Rem 122/GRA-4 and 150 feet of Wire W-120. Each end ofthe wire is equipped with a mating termination so that the wires from any number of reels can be combined to make uplonger antennas. Two small holes are provided in the reel handle for connection to the halyard.

c. The stainless steel measuring tape is 100 feet long.

d. RF Cable Assembly CG-692/U consists of 75 feet of RF Cable RG-8A/U having an impedance of 52 ohms. Thecable is terminated at one end with a male coaxial connector and at the other end with a special weather-tight antennaconnector for use with center-fed antennas. This cord is used for the center-fed Hertz antenna built with Antenna GroupAN/GRA-12.

e. The hook assembly consists of two snap hooks joined by a steel ring. One hook assembly is used for the center-fed Hertz antenna and also to fasten the halyard on the center mast to the special antenna connector on RF CableAssembly CG-692/U. Two hook assemblies can also be used to fasten the reel assemblies to the halyards if desired.

10. Running Spares

a. The following spares are supplied with Antenna Mast Assembly AB-86/GRA-4:

1 Guy Stake GP-111/G2 Guys MX-383/GRA-4 (red)2 Guy Plates MX--378/U2 hooks

b. No running spares are supplied with Antenna AS244/GRA-4.

TAGO 2189B 13

c. One spare hook assembly is supplied with Accessory Kit MX-1137/GRA-12.

11. Differences Between Antenna Groups AN/GRA-4 and AN/GRA-12

Each antenna group consists of an antenna and supporting mast sections. The two groups differ as follows:

a. Mast Section. Antenna Group AN/GRA-4 contains two Antenna Mast Assemblies AB-86/GRA-4, and AntennaGroup AN/GRA-12 contains three Antenna Mast Assemblies AB86/GRA-4. Antenna Group AN/GRA-12 is designedprimarily to make a center-fed Hertz antenna only, using all three mast assemblies.

b. Antenna Section. Antenna Group AN/GRA-4 contains one Antenna AS-244/GRA-4, and Antenna GroupAN/GRA-12 contains one Accessory Kit MX-1137/GRA-12. The differences between Antenna AS-244/GRA-4 andAccessory Kit MX1137/GRA-12 are shown in the following chart:

AS-244/GRA-4 used in MX-1137/GRA-12 used inItem AN/GRA-4 AN/GRA-12

RF cable (used for Contains 6 Cords CG- Contains one RF Cablecenter-fed Hertz 357/U, 50 ft long, 72 Assembly CG-692/U,antenna). ohms impedance. 75 ft long, 52 ohms

impedance.Insulator (used) for Contains one Insulator Contains one insulator

center-fed Hertz IL-4/GRA-4. as part of RF Cableantenna. Assembly CG-692/U

(permanently con-nected to cable).

Halyards. Contains two Halyards Contains no halyard inMX-516/GRA-4 in ad- addition to those in-dition to those included eluded in mast assem-in mast AB-86/GRA-4 blies (total 3 hal-(total 4 halyards). yards).

Wire W-128. Contains two 10-foot Contains no lengths oflengths in addition to Wire W-128 in addi-those included in mast tion to those includedassemblies (total of 4 in mast assemblieslengths). (total of 3 lengths).

Tuning unit. Contains one Antenna Tuning unit not in-Tuner TN-174/ eluded.GRA-4.

Hook assemblies (used Hook assemblies not in- Contains three hook as-for center-fed Hertz cluded (not required semblies.antenna). with Antenna Group

AN/GRA-4).

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CHAPTER 2INSTALLATION

12. Selecting Type of Antenna

a. General. When selecting the antenna, the basic concepts of good military radio communications as well as theoperating characteristics of each type of antenna should be taken into account. Table I summarizes the characteristics ofeach antenna.

b. Vertical Antennas. A vertical antenna can be used for both transmitting and receiving at distances up to 30 milesover open terrain and at frequencies of 1.7 to 2.0 mc. Radiation depends on ground waves. Antenna Mast AssemblyAB-86/GRA-4 can be used to make up a 40-foot vertical radiator (fig. 16) or, with a whip adapter, a 55-foot verticalradiator, as required. The vertical antenna must be located within 10 feet of the radio set.

c. Horizontal Antennas. In areas, such as jungles, where vegetation is very dense, vertical antennas are not usefulbecause all the ground wave is absorbed by the surrounding growth, and only very weak sky waves are transmitted. Thisnecessitates the use of a horizontal antenna and sky wave communication. The specific type of horizontal antenna to beused is determined by the conditions and terrain at the radio station and the frequency of the associated radio set. Thevarious types of horizontal antenna which can be made up from Antenna Group AN/GRA-4 and the characteristics ofeach are discussed below.

(1) Slanting wire antenna.

(a) If the station is located in a clearing, a slanting wire can be used as an antenna by attaching one endto the 40-foot mast or to a tall tree (fig. 6). If the operating frequency is relatively low, acomparatively long antenna must be used. (Frequencies lower than 3.1 mc require the use of tworeel assemblies.) Since a slanting wire antenna longer than 100 feet introduces excessive sag,height must be sacrificed. Therefore, it is advisable to use this antenna with operating frequenciesnot less than 4.5 mc.

(b) The slanting wire antenna is highly directional, and cannot be used very successfully forcommunication with more than one station.

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Figure 6. Slanting wire antenna.

(2) L-type antenna.(a) If the radio station is located in a clearing, the L-type antenna can be used with two mast assemblies

or with one mast assembly and a structural member as support (fig. 7).(b) The L-type antenna is most efficient when installed so that the horizontal portion is one-half wave

length and the down lead is one-quarter wave length. Since the mast assembly is 40 feet high andthe vertical portion should be as straight as possible, the antenna operates most efficiently at afrequency of 5.6 mc. At all other frequencies, a compromise must be made. The antenna shouldnot be used at frequencies higher than 5.8 mc. At frequencies lower than 3.1 mc, two reelassemblies must be used to make up the necessary length.

(3) Off-center-fed Hertz antenna.(a) If the station is located in a clearing where mast assemblies can be set up on each side, tile off-

centerfed Hertz antenna (fig. 8) can be used to advantage.The lead-in wire should be vertical, and its length should not exceed the length of the antenna; in nocase should it exceed 100 feet. This type of antenna can be used on all frequencies between 1.5and 11.0 mc.

(b) This antenna uses a single wire transmission line and depends on the ground for a return circuit.Therefore, good conducting ground is essential.

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(4) Center-fed Hertz antenna.

(a) If the station is concealed but a clearing exists within 300 feet, the center-fed Hertz (doublet) antenna(fig. 9)can be used with two mast assemblies as supports. The coaxial cable which serves as a feedshould be routed at a 90° angle to the antenna and should be kept to minimum length.

(b) The center-fed Hertz antenna is always one-half wave length long and is fed at the center. It can beused on frequencies from 1.5 to 18 mc.

(c) Since received signals are weaker than transmitted signals and may be further attenuated by a longtransmission line, it is better to use a separate receiving antenna located near the receiver.

Figure 7. L.-type antenna.

13. Siting

a. General. When choosing a location for setting up the mast assembly and antenna, the conditions listed in table Ishould first be taken into consideration. Location of the distant station also should be taken into account. Whencommunicating with two or more distant stations, the antenna should be located in a position favorable to the stationmost difficult to receive.

b. Vertical Antennas. The ideal location for erecting a vertical antenna is the center of a plateau having no naturalor artificial

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Figure 8. Off-center-fed Hertz antenna.

obstructions nearby. When possible, select a spot of dry ground having good drainage to provide a firm base for thestakes.

c. Horizontal Antennas. If the location of the communication center is not suitable for a vertical antenna, use ahorizontal antenna. Locate it in a clearing and determine its direction by the orientation at which it takes fullestadvantage of its radiation pattern. Since the radiation pattern of the half-wave antenna is broadside to the wire, theantenna should be erected with the wire broadside to the distant station. When two or more stations are to beconsidered, orient the antenna so that the broadside of the wire faces the station most difficult to receive. Note that bothlocation and orientation should be determined by the distant stations whenever possible.

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Table I. Characteristics of Various Antenna Arrangements

Terrain Recommended frequencyAntenna type characteristics Type of support (me) LimitationsVertical Open Mast assembly used as

radiator.1.7 to 2.0 Uses ground wave only. Must

be. within 10 feet of radio set.Slanting wire Large clearing near station. Mast assembly or tree. Not less than 4.5 Highly directional.L Clearing adjacent to station. 2 mast assemblies or 1 mast

assembly and structure.5.6 (ideal) or lower Lower than 3.1 mc requires

use of two reel assemblies.Lead-in as near to 90° verticalas possible.

Off-center-fed Hertz Clearing adjacent to station. 2 mast assemblies. 1.5 to 11.0 Length of lead-in cannotexceed antenna length norlength of 100 feet. Lead-in on90° vertical

Center-fed Hertz Clearing within 300 feet ofstation.

2 mast assemblies. 1.5 to 18 Uses coaxial cable. Mayrequire separate receivingantenna

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Figure 9. Center-fed Hertz (doublet) antenna, using Antenna Group AN/GRA-4.

14. Unpacking

a. Packaging Data for Antenna Group AN,/GRA-4. When packed for shipment, Antenna AS-244/GRA- is placed inBag BG-102-A with two copies of TM 11-2651. Each of the two mast assemblies is assembled in its carrying frame.Each of the three components is then placed in a separate corrugated carton. The end plates of the frame are protectedby corrugated end caps. A. corrugated filler is placed in the carton with the canvas bag. Each carton is then sealed, andthe three cartons are placed in a nailed wooden box which is secured with steel straps. The shipping box with itscontents is 15 inches high, 22 inches wide, and 53 inches deep. It weighs 210 pounds and has a volume of 10.1 cubicfeet.

b. Packaging Data for Antenna Group AN/GRA-12. When packed for shipment, the components of Antenna GroupAN/ GRA-12 are placed in two fiberboard cartons; one carton contains the 48 mast sections, and the other contains allthe other components.

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Figure 10. Center-fed Hertz (doublet) antenna, using Antenna Group AN/GRA-12.

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(1) Each mast section is wrapped in flexible corrugated paper and secured with gummed Kraft tape. The 48mast sections then are placed in a close-fitting fiberboard carton which is then sealed with water-resistantpressure-sensitive tape.

(2) Each remaining component is packaged individually as follows:

(a) Antenna Adapters MX-857/GRA-4, Frames MX1116/GRA-4 Hammers HM-1, Insulators MX384/GRA-4, Halyards MX-516/GRA-4, guy stakes hook assemblies, and Guy plates MX-378/U are wrapped inflexible corrugated paper and secured with gummed Kraft tape.

(b) Bag CW-206/GR is folded and tied with cotton tape, and Guys MX-381/GRA-4, MX-382/GRA-4, andMX-383/GRA-4 are wound into coils and tied in three places with cotton tape. The bag and guys arethen placed in individual sealed waterproof bags.

(c) Wire W-128 (10-foot lengths), Counterpoise CP-12, RF Cable Assembly CG-692/U, and the steeltape (100 feet) are individually wrapped in flexible corrugated paper and secured with gummed Krafttape. Each item is then placed in a sealed moisture-vaporproof bag.

(3) All the components listed in (2) above are tightly packaged in one fiberboard carton and all voids are filledwith corrugated paper to avoid shifting. The carton is then sealed with water-resistant pressure-sensitivetape.

(4) The two cartons packed with the equipment are approximately 16 inches high, 281/2 inches wide and 38inches deep. They weigh 250 pounds and have a volume of 11.1 cubic feet.

c. Removing Contents. When unpacking equipment in wooden boxes, perform all the steps outlined below. Whenunpacking equipment in cartons, omit the steps in (1) through (3) below.

(1) Cut and fold back the metal straps.(2) Remove the nails from the top and one side of the box with a nail puller. Remove the top and one side.

Do not attempt to pry them off because the equipment may become damaged.(3) Open the moistureproof barrier that covers the carton inside the box. Remove the carton.(4) Open the carton and the moisture-vaporproof barrier within the carton. Remove the inner cartons. Open

the inner cartons and remove the contents.

TAGO 2189B 22

(5) When unpacking the mast assembly, proceed as follows:

(a) Unfasten the two straps at the top of the unit and remove the three mast sections which rest in theracks on the end plates.

(b) Remove all guys, stakes, etc., from inside the frame.(c) Loosen and unhook the turnbuckle and cable which hold the end plates together.(d) Remove the end plates to free the remaining mast sections.(e) Remove the guy plates from the cable of the carrying frame.

(6) To unpack the antenna assembly, open the canvas bag and remove the technical manuals andcomponents.

d. Checking Unpacked Equipment. Inspect the equipment for damage possibly incurred during shipment. If theequipment has been damaged, refer to paragraph 2. Check the equipment against the packing list and against the tableof components in paragraph 5.

15. Installation of Most Assembly

a. General. When the location for the mast assembly (par. 12 and 13) has been chosen, drive the swivel stake onthe mast base into the ground at the selected point; use the hammer supplied.

b. Mast Sections and Guy Plates.

(1) Place the mast sections in a line on the ground (fig. 13) with the female end of each section pointingtoward the swivel stake.

Note. If the mast assembly is to be used as an antenna support, the direction in which theantenna will run should first be determined. The line of mast sections should be placedapproximately 135' counterclockwise from the direction of the horizontal antenna. The top guyplate should be positioned so that the odd hole will face toward the direction of the antennawhen the mast assembly is raised.

(2) Add the base insulator to the swivel stake and then add the mast sections one by one until five sectionshave been assembled. Allow the mast sections to rest on the ground.

(3) Place a guy plate on the male end of the fifth section.(4) Add five more mast sections to the first five sections and place a second guy plate on the male end of the

tenth mast section.(5) Add the last 6 sections to the first 10 and place the third guy plate on the last section.(6) If the 55-foot antenna is being used, add the whip adapter to the last mast section. Add the standard whip

TAGO 2189B 23

Figure 11. Packaging of Antenna Group AN/GRA-4.

antenna which consists of three Mast Sections MS-116, one MS-117, and MS-118 in that order.

Note. The whip antenna is not supplied with this equipment.

c. Stakes. The four stakes should be located 25 feet from the swivel stake and approximately 90' apart. Note thatthe letters assigned to the stakes in figures 13 and 14 and in the text below are inserted for purposes of illustration onlyand are not markings on the equipment.

TAGO 2189B 24

Figure 12. Packaging of Antenna Group AN/GRA-12

(1) Drive in stake A at the junction of the 10th and 11th mast sections. Tilt the stake away from the swivelstake at an angle of approximately 30'.

(2) Measure the distance between the swivel stake and stake A. Use a guy or the measuring tape.(3) Use this measurement and locate stakes B and C about 90° on either side of the swivel stake.(4) Drive in each stake at a 30' angle to the swivel stake.(5) Use the same measurement and locate stake D 90o from stakes B and C.(6) Drive in stake D at a 30' angle.

Figure 13. Assembling mast sections and positioning stakes.

d. Guys (fig. 14). The guys are color-coded for immediate identification: top, red; center, white; lower,blue. Each guy plate has four holes 90° apart for attaching the guys. A fifth hole is provided for connection of a halyardand should be kept in the direction of the antenna when the halyard is to be used. Connect the guys as follows:

(1) Connect the guys for stake A first. Attach the snap hook of each guy to the corresponding hole of the proper guyplate.

TAGO 2189B 25

(2) Stretch the guys out to stake B to measure for the correct adjustment. Adjust each guy by means ofFastener FT-9.

(3) Carry the free end of each guy back to stake A and fasten it, be careful not to tangle the ropes.(4) Attach the guys for stakes B and C. Attach each set of guys to the corresponding holes of the guy plates

and to stakes B and C; make the proper adjustment with the fittings. When tightening the guys, do notbend the mast pole.

(5) Connect three guys for stake D to the corresponding guy plates, and stretch the guys along the masttoward stake D. If a halyard is used, fasten the halyard pulley to the fifth hole of the top guy plate, and tiethe two ends of the halyard together to prevent the halyard from running through the pulley.

Figure 14. Attaching guys.

16. Raising Mast

a. Two men are required to raise the mast. One man stands near the swivel stake, holding the halyard, if used, andthe three free guys. The second man takes his position at the far end of the mast pole.

TAGO 2189B 26

b. The first man pulls on the free set of guys, being sure to keep more tension on the top guy so that the mast bowsslightly. At the same time, the second man raises the end of the mast.

c. The first man walks toward stake D while pulling on the guys. At the same time, the second man walks towardthe swivel stake, raising the mast pole as he goes.

d. When the mast is upright and the slack set of guys has become taut, the second man assists the first in securingand adjusting the free set of guys to stake D. The halyard, if used, should be released and allowed to hang freely at themast.

e. If further adjustment is necessary to bring the mast more nearly vertical, first slack off the guys which are tooshort, then tighten the guys that are too long, and finally tighten the guys that were slacked off.

f. If the mast assembly is to be used as a vertical radiator (fig. 16), use the counterpoise. Place the counterpoise atthe base of the mast assembly and attach the four radials to the stakes. Connect the lead-in wire of the counterpoise to agood ground. The binding post of the tuning unit or the ground used with the associated radio set may be used. Ifavailable, a long metal stake driven into the ground can be used. Attach the lead-in wire from the radio set or tuning unitto the binding post on the top of the base insulator.

Figure 15. Raising mast.

17. Determining Length of Antenna

a. Table II lists the different lengths of antenna to be used with various frequencies. Refer to paragraph 32 for adiscussion of the theory related to antenna length.

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Table II. Half-Wave Antenna Length

Freq Length Freq Length Freq Length(mc) (ft) (in.) (me) (ft) (in.) (me) (ft) (in.)1.5 312 0 5.6 81 1 9.7 45 11.6 292 6 5.7 79 7 9.8 44 71.7 275 4 5.8 78 2 9.9 44 11.8 260 0 5.9 76 10 10.0 43 81.9 246 4 6.0 75 5 10.1 43 22.0 234 0 6.1 74 1 10.2 42 102.1 222 11 6.2 72 11 10.3 42 52.2 212 8 6.3 71 8 10.4 42 02.3 203 6 6.4 70 6 10.5 41 72.4 194 10 6.5 69 4 10.6 41 22.5 186 10 6.6 68 2 10.7 40 82.6 179 6 6.7 67 1 10.8 40 42.7 172 8 6.8 66 0 10.9 40 02.8 166 5 6.9 65 0 11.0 39 72.9 160 6 7.0 64 0 11.1 39 23.0 155 0 7.1 63 1 11.2 38 113.1 150 0 7.2 62 2 11.3 38 63.2 145 0 7.3 61 4 11.4 38 23.3 140 6 7.4 60 5 11.6 37 113.4 136 4 7.5 59 6 11.6 37 63.5 132 4 7.6 58 8 11.7 37 23.6 128 6 7.7 67 11 11.8 36 113.7 124 11 7.8 57 1 11.9 36 73.8 121 6 7.9 56 4 12.0 36 43.9 118 4 8.0 55 6 12.1 36 04.0 115 4 8.1 54 10 12.2 35 84.1 112 4 8.2 54 1 12.3 35 54.2 109 5 8.3 53 5 12.4 35 14.3 106 10 8.4 52 8 12.5 34 104.4 104 4 8.5 62 0 12.6 34 74.5 101 11 8.6 61 5 12.7 34 44.6 99 7 8.7 50 10 12.8 34 04.7 97 5 8.8 50 2 12.9 33 104.8 95 4 8.9 49 6 13.0 33 64.9 93 4 9.0 48 11 13.1 33 25.0 91 5 9.1 48 4 13.2 33 05.1 89 6 9.2 47 8 13.3 32 85.2 37 8 9.3 47 2 13.4 32 65.S 86 0 9.4 46 8 13.5 32 45.4 84 4 9.5 46 1 13.6 32 05.5 82 8 9.6 45 7 13.7 31 1013.8 31 7 15.3 28 6 16.8 26 013.9 31 4 15.4 28 4 16.9 25 1014.0 31 1 15.5 28 1 17.0 25 714.1 30 11 15.6 27 11 17.1 25 614.2 30 8 15.7 27 8 17.2 25 414.3 30 6 15.8 27 7 17.3 25 214.4 30 2 15.9 27 5 17.4 25 014.5 30 0 16.0 27 2 17.6 24 10

TAGO 2189B 28

Table II. Half-Wave Antenna Length-Continued

Freq Length Freq Length Freq Length(mc) (ft) (in.) (mc) (ft) (in.) (mc) (ft) (in.)14.6 29 10 16.1 27 1 17.6 24 814.7 29 7 16.2 27 0 17.7 24 714.8 29 5 16.3 26 10 17.8 24 614.9 29 2 16.4 26 7 17.9 24 615.0 29 0 16.5 26 5 18.0 24 415.1 28 10 16.6 26 215.2 28 7 16.7 26 1

Figure 16. Mast assembly installed as a vertical radiator.

b. The following chart lists the points of measurement for the various types of horizontal antenna.

Type Measure

Slanting wire From junction of reel and halyard toradio set or tuning unit bindingpost

L-type, off-center-fed Hertz, or From one halyard fastener to othercenter-fed Hertz. halyard fastener.

TAGO 2189B 29

18. Installing Antenna, Using Antenna Group AN/GRA-4

a. Slanting Wire Antenna (fig. 6).

(1) General. The slanting wire antenna is usually one-half wave length long. Refer to paragraphs 12 and 13for information on locating and siting the antenna and to table II for the proper length. When measuringthe length, be sure to start at the transmitter, receiver, or tuning unit binding post and include the lead-inwire.

(2) Procedure. After the direction and location of the antenna have been chosen, install the antenna asfollows:

(a) If the 40-foot mast assembly is to be used as the support, locate the mast about one-half wavelength from the transmitter or receiver and erect the mast assembly (pars. 15 and 16). Fasten thehalyard to the top guy plate before raising the mast assembly.

(b) If a tree or similar support is used, first attach the pulley on the halyard to the support at the desiredheight. Locate the transmitter, receiver, or tuning unit approximately one-half wave length from thesupport.

(c) Fasten the antenna wire termination to the lead-in wire or tuning unit. Connect the lead-in wire or thetuning unit to the radio set.

(d) Fasten the insulator end of a second halyard about 6 inches from the end of the antenna wire (fig.17), and secure the halyard to a stake or to the transmitter or receiver. Adjust the halyard to take allthe strain of holding the antenna wire tightly. Allow the lead-in wire to sag, but do not allow it totouch the ground at any point.

(e) Unwind the wire of the antenna reel as follows (fig. 18):

1. Grasp the reel firmly in one hand and loosen the thumb nut at the center of the reel and on thewire clamp.

2. Remove the wire from the clamp.3. Walk slowly away from the transmitter, keeping the wire taut at all times. Hold your thumb on

the wire to prevent backlash.

(f) With the measuring tape, measure off the length of wire obtained in table II.

Note. The tape should be wiped off after use to prevent dirt and sand from entering and cloggingthe reeling mechanism.

TAGO 2189B 30

Figure 17. Attaching halyard to antenna wire.

Figure 18. Unwinding antenna wire from reel.

(g) Replace the wire in the wire clamp and tighten the thumb nut.(h) Tighten the thumb nut at the center of the reel.(i) Attach the insulator end of the other halyard to the reel (fig. 19).

TAGO 2189B 31

Figure 19. Attaching halyard to reel.

(j) Pull the free end of this halyard to raise the antenna and secure the halyard to a guy stake.

b. L-Type Antenna (fig. 7).

(1) General.

(a) The L-type antenna (par. 12c(2)) operates most efficiently at 5.6 me, having a down lead of 40 feetand the horizontal portion of the antenna equal to 80 feet. Refer to paragraph 13 for siting, and referto table II to obtain the required length.

(b) The L-type antenna is not recommended for use on frequencies higher than 5.8 mc. For frequenciesabove 3.1 me, one antenna reel is used. For frequencies lower than 3.1 mc, remove the wire fromone reel and connect it in series with the wire on a second reel to make up the required length (fig.20).

(2) Procedure.

(a) Erect the two 40-foot mast assemblies or one mast assembly and a similar support one-half wavelength plus 20 feet apart (paras. 15 and 16).

(b) Fasten the pulley of a halyard at a height of 40 feet to the similar support, if used.(c) Fasten the antenna wire termination to the tuning unit and connect the tuning unit to the radio set.(d) Starting at the end of the lead-in wire, measure and unwind 40 feet of wire for the down lead (a(2) (e)

above). At this point, attach the fastener of the near halyard insulator to the antenna wire (fig. 17).(e) Unwind the antenna wire until the length from one halyard fastener to the other is one-half wave

length (table II). If necessary, use the wire from two reels by removing the wire from one reel andattaching it to the wire on a second reel (fig. 20).

TAGO 2189B 32

Note. To remove the wire from a reel, loosen the off-center thumb nut on the reel, slide thethumb nut and the wire termination toward the adjacent hole (fig. 18). Slip the nut through thehole and remove the wire from the reel. To rewind the wire on the reel, refer to paragraph 34a(1)(d).

(f) Place the wire in the wire clamp and tighten the thumb nut of the clamp and the nut at the center ofthe reel.

(g) Fasten the remaining halyard insulator to the reel (fig. 19).(h) Raise the antenna by pulling the free end of each halyard until the antenna wire is taut. Tie each

halyard to a guy stake or other device if a similar support is used.

c. Off-Center-Fed Hertz Antenna (fig. 8).

(1) General. The off-center-fed Hertz antenna is a half-wave antenna which uses a single wire feeder. Theimpedance of a single wire feeder is approximately 500 ohms. The feeder should be connected to the

Figure 20. Connecting antenna wire from two reel assemblies.

TAGO 2189B 33

Figure 21. Connecting the antenna wire from three reel assemblies.

antenna at a 500-ohm point. This point can be found by multiplying the antenna length (table II) by .361.The result is the number of feet from either end of the antenna to this point where the feeder should beconnected. Refer to table I for siting.

(2) Procedure.

(a) Erect the two 40-foot mast assemblies, with halyards, one-half wave length plus 20 feet apart (paras.15 and 16).

(b) Fasten the wire terminations of three antenna reels together (fig. 21). Two of the wires serve as theantenna, and the third serves as the feeder.

(c) Unwind and measure one wire to obtain the length to the 500-ohm point ((1) above). This is theshorter side of the antenna.

(d) Unwind the second wire until the length of the first wire plus the second wire equals one-half wavelength (table II).

TAGO 2189B 34

Figure 22. Connections to Insulator IL-4/GRA-4.

(e) Unwind 40 feet of wire from the third reel.(f) Place each wire in its corresponding wire clamp and tighten all thumb nuts.(g) Fasten the first and second reels to the insulator end of the respective mast halyards (fig. 19).(h) Pull the free end of each halyard until the antenna is raised. Secure each halyard to the guy fastener

at one of the stakes.(i) Fasten the insulator end of a third halyard to the third reel and secure the halyard to the transmitter,

receiver, or to a stake in the ground. Adjust the length of the feeder to remove all slack.(j) Fasten one end of the insulated lead-in wire of the tuning unit lead-in under the thumb nut on the reel

wire clamp. Connect the other end of the tuning unit lead-in to the transmitter or receiver bindingpost.

d. Center-Fed Hertz (Doublet) Antenna (fig. 9).

(1) General. The center-fed Hertz (doublet) antenna is a half-wave antenna fed at the center by means of a

TAGO 2189B 35

Figure 23. Tuner TN-174/GRA-4, front view.

coaxial cable of 72 ohms impedance. Refer to table I for siting.

(2) Procedure.

(a) Erect the two 40-foot mast assemblies, with halyards, one-half wave length plus 20 feet apart (paras.15 and 16).

(b) Connect the wire terminations of the two reel assemblies to Insulator IL-4/GRA-4 by means of thethumb nuts on the insulator (fig. 22).

(c) Attach Cord CG-357/U to the coaxial connector in the insulator.

TAGO 2189B 36

(d) Unwind and measure each antenna wire to a length equal to slightly less than one-half the valueobtained from table II.

(e) Check the overall length of the two wires plus the insulator. Adjust if necessary, and be sure to keepthe insulator centered.

(f) Attach each reel to the insulator of the respective mast halyard (figs. 9 and 19).(g) Raise the antenna by pulling the free end of each halyard. Secure each halyard to the guy fastener

of a ground stake.(h) Connect enough coaxial cable to the coaxial feed to reach the transmitter.

e. Tuning Unit. Tuner TN-174/GRA-4 (fig. 23) is used with slanting wire antennas (fig. 6). To connect the tuningunit, proceed as follows (refer to a above):

(1) Attach the tuner lead-in wire to the antenna wire termination.(2) Attach the connecting wire from the transmitter or receiver to the other tuner lead-in wire.

Figure 24. Connections to RF Cable Assembly CG-692/U.

TAGO 2189B 37

Figure 25. Details of tying wire to insulator.

19. Installing Antenna, Using Antenna Group AN/GRA-1 2

a. General. The only type of antenna normally built with Antenna Group AN/GRA-12 is the center-fed Hertzantenna. It is a half-wave antenna fed at the center by means of a coaxial cable having a characteristic impedance of 52ohms.

b. Procedure.

(1) Erect the two end mast assemblies one-half wave length plus 20 feet apart with halyards (paras. 15 and16).

(2) Erect the center mast assembly in line with the other two and exactly halfway between them with thehalyard.

(3) Fasten the wire terminations of the two reel assemblies to the cable assembly by tying the wire to theinsulator as shown in figures 24 and 25.

(4) Attach the halyard of the center mast to the cable assembly by means of one hook assembly as shown infigure 25

(5) Unwind and measure each antenna wire to a length slightly less than one-half the value obtained fromtable II.

TAGO 2189B 38

(6) Check the overall length of the two wires plus the connector. Adjust it if necessary; be sure to keep theconnectors and the RF cable assembly centered by raising halyard of the center mast first.

(7) Attach each reel to the insulator of the respective mast halyard (fig. 19).(8) Raise the antenna by pulling the free end of each halyard. Secure each halyard.

20. Tuner TN-174/GRA-4 Control

The tuning unit (fig. 26) has a single tuning capacitor, which is used to adjust the reactance of the feeder line. Aneon bulb indicates resonance during antenna loading. When using the tuning unit for transmitting or receiving, adjustthe tuning control slowly until the neon bulb glows at maximum brilliance.

Figure 26. Tuner TN-174/GRA-4, interior view.

TAGO 2189B 39

CHAPTER 3

ORGANIZATIONAL MAINTENANCE

Note. Organizational maintenance is performed at first and second echelon. First echelonmaintenance is operators maintenance; second echelon maintenance is unit repairmen’smaintenance.

Section I. FIRST ECHELON (OPERATOR) MAINTENANCE

21. Scope of Operator's Maintenance

The following is a list of maintenance duties normally performed by operator of Antenna Groups AN/GRA-4 andAN/GRA-12. These procedures do not require special tools or test equipment.

a. Preventive maintenance (par. 23).

b. Replacement of defective pilot lamp (par. 30).

c. Checking cable connections.

22. Tools, Materials, and Test Equipment Required

No special tools or test equipment is supplied with Antenna Group AN/GRA-4 or AN/GRA-12.. It may benecessary, however, to make continuity checks or an insulation test during trouble shooting. Use an ohmmeter formaking continuity checks, and use a megohmmeter for insulation tests. Multimeter ME-77/U should be used for thesechecks.

23. Operator's Preventive Maintenance

DA Form 11-238 (fig. 27) is a preventive maintenance checklist to be used by the operator. Items not applicableto the antenna group are lined out in the figure. Instructions for the use of the form appear on the back of the form.

Warning. Prolonged breathing of cleaning compound fumes is dangerous. Make sure thatadequate ventilation is provided. Cleaning compound is flammable; do not use near a flame.

TAGO 2189B 40

Figure 27. DA Form 11-238.

24. Visual Inspection

Check all the electrical connections for tightness, and check the lead-in wires for possible short or open circuits.Check insulators for cracks, chips, or other defects.

TAGO 2189B 41

Section II. SECOND ECHELON (UNIT REPAIRMAN) MAINTENANCE

25. Scope of Unit Repairman's Maintenance

The following is a list of maintenance duties performed by the unit repairman for Antenna Groups AN/GRA-4 andAN/GRA-12. The scope of these instructions has been determined by the available tools, materials, test equipment,spare parts and the MOS of the unit repairman.

a. Preventive maintenance (par. 27).

b. Troubleshooting (par. 29).

c. Replacement of parts (par. 30).

26. Tools, Materials, and Test Equipment Required

The tools, materials and test equipment required for unit repairman's maintenance are listed below.

a. Tools. Tool Equipment TE-41 is required for unit repairman's maintenance.

b. Materials.

Cleaning Compound (Federal stock No. 7930-395-9542)Cheesecloth, lint-free*Sandpaper, No. 000*

c. Test Equipment. Multimeter ME-77/U is used for testing.

27. Unit Repairman's Preventive Maintenance

DA Form 11-239 (fig. 28) is a preventive maintenance check list to be used by the unit repairman. Items notapplicable to the equipment are lined out in the figure. References in the ITEM block in the figure are to paragraphs thatcontain additional maintenance information pertinent to the particular item. Instructions for the use of the form appear onthe back of the form.

Warning. Disconnect all power before performing preventive maintenance. When power to theequipment is disconnected, the antenna tuning capacitor may retain voltage of dangerouspotential. Before touching exposed electrical parts, short-circuit the part to ground. Whenmaintenance is completed, reconnect the power, and check for satisfactory operation.

28. Unit Repairman's Visual Inspection

Before operating the equipment, inspect the following for obvious defects:

a. Check the capacitor and pilot light on the antenna tuner for looseness.

*Part of Tool Equipment TE-41.

TAGO 2189B 42

Figure 28. DA Form 11-239.

TAGO 2189B 43

b. Check the transmission line from the radio set to the antenna.

c. Check the mast assemblies for any damage or weakness caused by rain, wind, storms, etc.

d. Check all connections between the radio set and antenna.

29. Troubleshooting

Shut down the power at the transmitter-receiver; disconnect the power end of the lead-in wire, and proceed asfollows:

a. No Output. Lack of output usually is caused by a short or an open circuit.

(1) Mast assembly.

(a) If the mast assembly is used as a vertical radiator, check for continuity at the junction between thelead-in wire and the lowest mast section; use the low scale of the ohmmeter. The reading should beclose to zero.No reading or a high reading indicates that the lead-in wire is open or defective and must be repairedor replaced.

(b) Check continuity through each mast section. A high reading indicates poor contact, probably causedby corrosion. If the mast sections need cleaning, disassemble the mast sections (para. 34) andremove corrosion with No. 000 sandpaper.

(2) Antenna assembly. Use the low scale of the ohmmeter and check continuity between the lead-in wire andthe radiating components. If Cord CG-357/U or RF Cable Assembly CG-692/U is used, check thecontinuity from both conductors. The reading should be close to zero. A higher reading probably indicatesa defective cord. Replace the cord.

b. Weak Output. Weak output may be caused by poor adjustment of the tuning unit, a poor connection, or leakage.Check the adjustment of the tuning unit (par. 20). Check all components for natural obstructions which may form a pathto ground (foliage, fungus, etc). Check all connections for tightness and all insulators for leakage.

Note. A weak output also may be caused by incorrect installation. Check measurements madein determining the length of the antenna (table II).

(1) Mast Assembly. Make the chocks outlined in a(1) above.

(2) Antenna assembly.

(a) Use the low scale of the ohmmeter and check the continuity between the lead-in wire and theradiating components. If Cord CG-357/U or RF Cable Assembly CG-692/U is used, check the

TAGO 2189B 44

continuity from both conductors to the radiating components. The reading should be close to zero.A higher reading probably indicates corrosion of the radiating elements or coaxial fittings. Clean theantenna wire and the fittings.

Note. Disconnect the cord before making the following measurement.

(b) Use the multimeter to check the insulation resistance between the inner and outer conductors ofCord CG-357/U or RF Cable Assembly CG-692/U. The reading should be at least 10 megohms. Ifthe reading is 0, the cord is probably defective. If the reading is less than 10 megohms but wellabove 0, lower the antenna, remove the cord from the insulator, and test the insulator, cord, andradiating components separately.

30. Replacement of Parts

a. Mast Assembly. If any component of the mast assembly becomes defective, replace it with a new componentfrom the spare parts.

b. Antenna Tuner.

(1) The only readily replaceable part of the antenna tuner is lamp bulb E1 in the tuning unit. Replace asfollows:

(a) Unscrew the knurled jewel lens on the front of the tuning unit.(b) Unscrew the bulb and replace it with a new one.(c) Replace the lens.

(2) The only item of the antenna tuner which can be readily repaired is the coaxial cable (fig. 29).

(3) Radio Frequency Cable RG-59A/U has four layers-an outer jacket, copper braid, polyethylene insulation,and a copper conductor. To install a connector on the end of a cable, proceed as follows:

(a) Remove 3/4 inch of the outer jacket.(b) Disassemble the connector (fig. 29).(c) Slide the threaded nut over the cable.(d) Slide the thin washer over the cable.(e) Slide the rubber gasket over the cable, allowing 1/16 inch of the outer jacket to protrude.(f) Slide the chamfered sleeve over the copper braid.(g) Flare the braid around the sleeve.(h) Remove the excess braid so that it is even with the outer edge of the chamfer.(i) Bare tile conductor by removing 3/16 inch of insulation from the end of cable.

TAGO 2189B 45

(j) Slide the contact over the conductor and solder through the solder hole; file smooth.(k) Insert the cable into the assembly shell.(l) Tighten the nut securely. When the cable and connector are properly assembled, the socket tip

should be flush with, or not more than 1/32 inch beneath, the edge of the coupling.

Figure 29. Cross section of coaxial cable and connector.

c. Accessory Kit.

(1) There are no readily replaceable parts of the accessory kit.(2) The only item of the accessory kit that can readily be repaired is the RF cable assembly.(3) Radio Frequency Cable RG-8A/U and Radio Frequency Cable RG-59/U are similarly constructed and a

connector can be replaced as outlined in b(3) above.(4) The antenna connector is a sealed weatherproof unit and should not be taken apart unless absolutely

necessary. To open the unit, the old sealing compound should be removed completely and a suitablesealing compound should be used when reassembling the unit. A cross-sectional drawing of the unit isshown in figure 30.

TAGO 2189B 46

Figure 30. Cross section of antenna connector used in Antenna Group AN/GRA-12.

TAGO 2189B 47

CHAPTER 4

THEORY

31. Circuit Theory

a. General. Five different types of antenna installation are available with Antenna Group AN/GRA-4: vertical,center-fed Hertz, off-center-fed Hertz, L-type, and slanting wire. With Antenna Group AN/GRA-12, the center-fed Hertzantenna is the only one normally constructed. The five types of antenna installation used are variations of the basic half-wave antenna and vary fundamentally only in the manner of installation and in the method of feeding the signal from thetransmitter to the antenna or from the antenna to the receiver. The characteristics of transmitting and receiving antennasare similar, and therefore a good transmitting antenna will also function well for reception. Certain practical limitations onthe use of the same antenna for both transmitting and receiving are explained below.

b. Basic Half-Wave Antenna. During transmission, a radio-frequency current in a conductor produces anelectromagnetic field which is radiated. During receiving periods, an electromagnetic field which is cut by a conductorwill cause a current flow in the conductor. If the length of the conductor wire is equal to half the wave length of theelectromagnetic wave, the result is a half-wave antenna. In a half-wave antenna, current is always maximum at thecenter and minimum at the ends, while voltage is minimum at the center and maximum at the ends (fig. 31). Impedanceis minimum at the center and maximum at the ends. The impedance at the center of a half-wave antenna isapproximately 72 ohms, and the impedance at the ends is approximately 2,500 ohms. The current distribution in theantenna is always the same regardless of the amount of current flow, but the amplitude of the current at any point on theantenna varies directly with the amplitude of the signal voltage.

c. Computing Antenna Length. An antenna, when properly tuned, is a resonant circuit and acts the same as anyother resonant circuit, such as the tank circuit in a radio receiver or transmitter. The wire used to make up the antennahas a certain amount of inductance per foot and a certain amount of distributed capacitance per foot. When the wire is

TAGO 2189B 48

Figure 31. Current and voltage distribution in a half-wave antenna.

placed above the ground, there is a small amount of capacitance between the wire and ground. When the inductivereactance of the wire is equal to the capacitive reactance of the wire, the antenna is resonant. Hence, a half-waveantenna, when cut to the correct length, presents a resistive load to the transmitter. The formula for determining thephysical length of an antenna is—

300,000,000 = Length in meters, or for a half-wave antenna the formula becomes: 492 = Length in feetFreq in cycles Freq in mc

The above formula gives the natural resonant frequency of a solid conductor in free space and assumes zero resistancein the conductor. The physical length of an antenna is affected by its height above ground and by the size and type ofwire used for its construction. Table II is a half wave length chart. The lengths in the chart are correct when using WireW-120 with a reel on either or both ends.

d. Directive Patterns (fig. 32).

(1) General. Maximum radiation occurs at the center of a half-wave antenna, because the current is greatestat that point. Little radiation takes place at the ends because the current is minimum there. Ideally, theradiation is at right angles to the plane of the antenna wire

TAGO 2189B 49

and completely encircles the conductor. The resulting antenna pattern, therefore, can be compared to adoughnut with the radiator passing through its center (A, fig. 32).

(2) Vertical half-wave antenna pattern. The vertical half-wave antenna radiates equally in all directions in thehorizontal plane. B shows the field pattern in the horizontal plane which results from a vertical half-waveantenna. The field pattern is a circle and the field strength is the same in any horizontal direction from theantenna wire. Although there is no vertical radiation along the direct line of the axis of the vertical half-wave, there are different amounts of radiation at different angles to the line of the antenna axis. C shows across section of the doughnut-shaped pattern. It is readily seen that along line OA, there is little radiation,while there is some radiation along line OB, and even more along line OC.

(3) Horizontal half-wave antenna pattern. For a horizontal half-wave antenna, the doughnut-shaped pattern inA applies if rotated 90o. D shows half of the doughnut-shaped pattern for the horizontal half-wave antenna.As in the vertical antenna, maximum radiation occurs in a plane perpendicular to the center line of theantenna, and as the plane angle decreases from the perpendicular, the radiation also decreases. Thus,there is considerable radiation in planes other than the horizontal. This radiation travels upward, strikesthe ionosphere, and bounces back; this results in propagation of the wave over considerable distances.This type of wave propagation is called sky wave. At high frequencies, the radiation is not reflected by theionosphere since it pierces the ionosphere and continues into outer space. The relative length of thevectors illustrates the variation of the amount of radiation with the change in plane angle. The directivepattern of the horizontal half-wave antenna is bidirectional in the horizontal plane and the antenna shouldbe oriented in the direction of maximum signal strength.

32. Antenna Circuits

a. Vertical Antenna.

(1) The vertical antenna is a variation of the basic half-wave antenna. The mast represents a quarter wavelength of the radio signal, and the other quarter wave

TAGO 2189B 50

Figure 32. Radiation pattern of a half-wave antenna.

length is supplied by a ground image to make up the required half-wave antenna. The single-wire feed lineis connected to the binding post at the base of the mast assembly, which is insulated from ground byInsulator MX-384/GRA-4. Good contact with ground is secured by the use of Counterpoise CP-12. Thistype antenna may be compared to a spring which, when vibrating at a given frequency, will continue tovibrate at that frequency, even if half of it is removed. In the case of the antenna, the missing half of theantenna is supplied by what can be regarded as the image of the radiating portion in ground. Thedistribution of current, voltage, and impedance in the radiator is the same as that of one-half of the

TAGO 2189B 51

simple half-wave antenna. The grounded vertical antenna is advantageous at low frequencies, because itreduces the total physical length of the antenna required by one-half. At the low frequencies used, thephysical length required for a full half-wave antenna becomes impractical. The physical length of thevertical grounded antenna may be more than a quarter wave length, but it must be an odd number ofquarter wave lengths if resonance is to be obtained at the base where the feed line is connected. If theantenna is over. a quarter wave length high, but less than a half wave length, the input at the base will beinductive, and will require the addition of capacitance in series with the feed to make the input resonant.The tuning unit is used for this purpose (par. 33).

(2) The vertical grounded antenna uses the antenna mast assembly as the radiator. This antenna is suitablefor both transmitting and receiving over short ranges (0 to 30 miles) at low frequencies of 1.7 mc to 2.0 mc.The radiation pattern of the vertical antenna is nondirectional in a horizontal plane and the signal travelsclose to the earth. Hence, this antenna is most efficient in fairly open terrain, because the radiation patternmight be distorted by large masses such as buildings, mountains, heavy foliage, and undergrowth whichtend to absorb the signal.

b. Horizontal Antennas. In the jungle and other locations where vegetation is dense, the vertical antenna cannot beused, because all the ground wave is absorbed. This necessitates the use of a horizontal antenna and sky wavecommunication.

(1) Center-fed Hertz antenna. The center-fed Hertz (doublet) antenna is always one-half wave length and isfed at the center by coaxial cable. This antenna can be used on all frequencies from 1.5 me to 18.0 mc. Itconsists of two lengths of wire, each a quarter wave length at the operating frequency. The center-fedHertz antenna is similar to the vertical antenna described in a above, except that the image supplied by theground in the vertical antenna is replaced here by an actual physical quarter wave length of wire. Thetransmission line is a low-impedance coaxial cable which is connected to the low-impedance point at thecenter of the antenna. Current and voltage distribution is the same as that described for the simple half-wave antenna; current is maximum at the center and zero at the ends, and voltage

TAGO 2189B 52

is maximum at the ends and minimum at the center. Because the antenna is independent of ground, it canbe installed far above the surface of the earth. The center-fed Hertz antenna is the most efficient radiatorand should be used whenever possible. It can be used to particular advantage if the station is concealedand a clearing is available for mounting the antenna at a maximum distance of 300 feet. The coaxialcable should leave the antenna at a 90° angle and should be kept short. The cable should be laid out asstraight as possible and not piled up. When a length of coaxial cable is used on good-conducting ground,there is a loss of received signal caused by the reactance of the line, and this loss cannot be tuned out atthe receiver. When transmitting, this reactance is eliminated by the tuning unit, as explained below.Therefore, if a long transmission line is used with the center-fed Hertz antenna, it is advantageous to use aseparate receiving antenna.

(2) Off-center-fed Hertz antenna. The off-center-fed Hertz antenna consists of a half wave length of wire fedby means of a single-wire feeder. This antenna may be used on all frequencies in the range of 1.5 mc to11.0 mc. The distribution of current, voltage, and impedance is the same in this antenna as in the center-fed Hertz antenna. The impedance of a single-wire feeder is approximately 500 ohms, and the feeder istherefore, connected at a 500-ohm point on the antenna. The point at which the feeder is connected to theantenna can be found by multiplying the antenna length by .361; the resulting figure is the number of feetfrom one end of the antenna to the feeder. The directive pattern of the off-center-fed Hertz antenna is thesame as that of the center-fed Hertz antenna.

(3) L-type antenna. The L-type antenna is similar to the off-center-fed Hertz antenna. It consists of a halfwave length of wire fed by means of a single-wire feeder. The distribution of current, voltage, andimpedance is the same as in the half-wave antenna (par. 31). The feeder is connected at one end, a high-voltage, maximum-impedance point. For most efficient matching, therefore, the feeder should be one-quarter wave length, and should be exactly perpendicular. A feeder of one-quarter wave length shows acontinuity of the standing wave current with that of the antenna and causes a minimum of radiation loss.

TAGO 2189B 53

Any other length of feeder causes a mismatch and tends to set up a radiation field about the feeder whichinterferes with the desired radiation of the antenna. Since the supporting masts are 40 feet in height andthe feeder must be one-quarter wave length, this antenna is most efficient at one frequency (5.6 mc); at allother frequencies, a compromise must be made. It is not advisable, however, to use the L-type antennaon frequencies higher than 5.8 mc. The directive pattern of this antenna, as in the other horizontal half-wave antenna, is bidirectional in the horizontal plane with maximum radiation in a line perpendicular to thecenter of the antenna.

(4) Slanting wire antenna. The slanting wire antenna is an adaptation of the horizontal antenna. It is usuallyone-half wave length. and is fed at the lower end, connecting directly to the transmitter, receiver, or tuningunit at that point. The measurement of the antenna length should start at the transmitter, receiver, ortuning unit binding post. The slanting wire antenna is not suitable for use on frequencies below 4.5 mcwhen using a 40-foot mast, because the excessive sag which results with wire lengths over 100 feet tendsto reduce the effective height of the antenna and lower its efficiency. Distribution of current, voltage, andimpedance is the same in this antenna as in the other half-wave antennas. This antenna is highlydirectional; radiation takes place at right angles to the antenna wire, in a skyward direction.

33. Tuner TN-174/GRA-4(fig. 33)

Although the theoretical length of a half-wave antenna can be computed exactly for any given frequency, theactual physical length of antenna which operates most satisfactorily for the same frequency may vary somewhat fromthis computed figure. Best operation is obtained when the impedance of the feeder line is matched perfectly to theimpedance of the antenna and maximum current is present in the antenna standing wave. This condition is known asresonance. The discrepancy between the computed wave length and the optimum physical wave length is due to certainvariable factors, such as the resistance of the antenna wire, the loading effects of interference from surrounding objects,etc. Since the optimum length of line cannot be computed readily, some means of tuning the line to resonance must beprovided. This is accomplished by means of the tuner. The tuner consists of a 12 to 244-micromicrofarad (µµf) variablecapacitor

TAGO 2189B 54

housed in a metal box, with a neon lamp connected in parallel across it. The tuner is then connected in series with theantenna lead-in. Tuning the capacitor varies the amount of reactance in the line, making it possible to adjust for theresonant condition by actual experiment. Resonance is indicated by the neon lamp which glows at maximum brilliancewhen the line is in the resonant condition.

Figure 33. Tuner TN-174/GRA-4, schematic diagram.

TAGO 2189B 55

CHAPTER 5

SHIPMENT, LIMITED STORAGE, AND DEMOLITION

Section I. SHIPMENT AND LIMITED STORAGE

34. Disassembly of Equipment

Warning. Shut all power off before performing any disassembly.

a. Antennas. To disassemble any of the various antennas, follow the instructions given below:

(1) Slanting wire antenna.

(a) Disconnect the lead-in wire from the transmitter, receiver, or tuning unit.(b) Release the tied ends of the halyards and lower the antenna slowly; be careful not to damage the

insulators.(c) Unfasten the antenna wire or wires, lead-in wire, and the reel from the insulator ends of the halyards.(d) Wind the antenna wire onto each reel; use one hand to hold the reel against the body and to guide

the wire and the other hand to turn the handle.

Caution: Improper winding will result in kinks, which will render the wire useless.

(e) Remove the pulley support for the upper halyard.(f) Remove the ground stake and wipe clean.(g) Coil and bind the halyards.

(2) L-type antenna. Follow the instructions in (1) (a) through (d) above, and then proceed as follows:

(a) Tie the two ends of the mast halyard to prevent the free end from running through the pulley.(b) Remove the pulley support for the other halyard.(c) Coil and bind the halyard.

(3) Off-center-fed Hertz antenna. Follow the instructions in (1) (a) through (d) above, and then proceed asfollows:

(a) Remove and clean the ground stake.(b) Coil and bind the halyards.

TAGO 2189B 56

(4) Center-fed Hertz (doublet) antenna.

(a) Disconnect Cord CG-357/U or Rf Cable Assembly CG-692/U from the transmitter.(b) Release the tied ends of the halyards and lower the antenna slowly; be careful not to damage the

insulators.(c) Unfasten the antenna wire terminations from the center insulator and unfasten the reels from the

insulator ends of the halyards.(d) Wind the antenna wire onto each reel.(e) Unfasten the cable from the center insulator and coil the cable as follows:

1. Make one coil and tie coil with friction tape.2. Using both hands, coil the remainder of the cable.

Note. With Antenna Group AN/GRA-12, the centering insulator (Connector CC-51) is part of thecable assembly and is coiled with the cable.

(f) Tie the two ends of each halyard to prevent the free end from running through the pulley.

b. Mast. To lower and disassemble the mast, follow the instructions given below:

(1) Disconnect and remove the counterpoise.(2) Remove all three guys from one stake located at a 90' angle to the pivot pin of the swivel stake.(3) Hold ail three guys firmly and walk slowly toward the mast. As the antenna tilts, the pull on the guys will

become stronger.(4) Brace yourself firmly while walking. Continue until the mast pole reaches the ground.(5) To disassemble the mast pole, reverse the assembly instructions given in paragraph 15.(6) Remove all stakes, including the swivel stake. Clean the stakes and plate.(7) Coil and bind the halyard, if used, and each guy.

35. Repacking for Shipment or Limited Storage

a. The exact procedure in repacking for shipment or limited storage depends on the material available and theconditions under which the equipment is to be shipped or stored. Refer to paragraph 14 and follow the instructions inreverse order.

b. Pack the components in corrugated cartons. Protect the components with a waterproof paper barrier. Seal theseams of the paper barrier with a waterproof sealing compound or tape. Pack the protected components in a woodencase.

TAGO 2189B 57

Section II. DEMOLITION OF MATERIAL

36. Authority for Demolition

Demolition of the equipment will be accomplished only upon the order of the commander. The destructionprocedures outlined in paragraph 37 will be used to prevent further use of the equipment.

37. Methods of Destruction

a. Smash. Smash the tuning unit and insulators; use sledges, handaxes, pickaxes, hammers, crowbars, or heavytools.

b. Cut. Cut wires, halyards, guys, bag, counterpoise; use axes, handaxes, or machetes.

c. Burn. Burn cords, halyards, guys, and technical manuals; use gasoline, kerosene, oil, flame throwers, orincendiary grenades.

d. Bend. Bend mast sections, stakes, whip adapter, carrying device, reels, and measuring tape.

e. Explode. If explosives are necessary, use firearms, grenades, or TNT.

f. Dispose. Bury or scatter the destroyed parts in slit trenches, foxholes or other holes, or throw them into streams.

TAGO 2189B 58

[AG 413.44 (3 Oct 56)]

By Order of Wilber M. Brucker, Secretary of the Army:

MAXWELL D. TAYLOR,General, United States Army,

Official: Chief of Staff.

JOHN A. KLEIN,Major General, United States Army,

The Adjutant General.

Distribution:

Active Army:

CNGB (1) US Army Tng Cen (2)ASA (3) POE (OS) (2)Tec Svc, DA (1) except Trans Terminal Comd (2)

CSIGO (30) Army Terminals (2)Tec Svc Bd (1) OS Sup Agencies (2)Hq CONARC (5) Army Elct PG (1)CONARC Bd (Incl ea Test Sig Fld Maint Shops (3)Sec) (1) Sig Iab (5)Army AA Comd (2) ACS (3)OS Maj Comd (5) Mil Dist (1)OS Base Comd (5) Units org under fol TOE:Log Comd (5) 11-7C, Sig Co, Inf Div (2)MDW (1) 11-16C, Hq&HqCo, Sig Bn, CorpsArmies (5) or Abn Corps (2)Corps (2) 11-57C, Armd Sig Co (2)Ft & Cp (2) 11-127R, Sig Rep Co (2)Sp Wpn Comd (2) 11-128C, Sig Depot Co (2)Army Cml Cen (4) 11-500R, Sig Svc Org (2)Gen & Br Svc Sch (5) 11-557C, Abn Sig Co (2)

except Sig Sch (25) 11-587R, Sig Base Maint Co (2)Gen Depots (2) except 11-592R, Hq&Hq Co, Sig Base

Atlanta Gen Depot Depot (2)(None) 11-597R, Sig Base Depot Co (2)

Sig Sec. Gen Depots (10)Sig Depots (17)

NG: State AG (6); units---same as Active Army except allowance is one copy to each unit.

USAR: None.

For explanation of abbreviations used, see SR 320-50-1.

U.S. GOVERNMENT PRINTING OFFICE : 1991 0 - 281-486 (43154)

TAGO 2189B 59

The Metric System and Equivalents

Linear Measure Liquid Measure

1 centiliter = 10 milliters = .34 fl. ounce1 centimeter = 10 millimeters = .39 inch 1 deciliter = 10 centiliters = 3.38 fl. ounces1 decimeter = 10 centimeters = 3.94 inches 1 liter = 10 deciliters = 33.81 fl. ounces1 meter = 10 decimeters = 39.37 inches 1 dekaliter = 10 liters = 2.64 gallons1 dekameter = 10 meters = 32.8 feet 1 hectoliter = 10 dekaliters = 26.42 gallons1 hectometer = 10 dekameters = 328.08 feet 1 kiloliter = 10 hectoliters = 264.18 gallons1 kilometer = 10 hectometers = 3,280.8 feet

Square MeasureWeights

1 sq. centimeter = 100 sq. millimeters = .155 sq. inch1 centigram = 10 milligrams = .15 grain 1 sq. decimeter = 100 sq. centimeters = 15.5 sq. inches1 decigram = 10 centigrams = 1.54 grains 1 sq. meter (centare) = 100 sq. decimeters = 10.76 sq. feet1 gram = 10 decigram = .035 ounce 1 sq. dekameter (are) = 100 sq. meters = 1,076.4 sq. feet1 decagram = 10 grams = .35 ounce 1 sq. hectometer (hectare) = 100 sq. dekameters = 2.47 acres1 hectogram = 10 decagrams = 3.52 ounces 1 sq. kilometer = 100 sq. hectometers = .386 sq. mile1 kilogram = 10 hectograms = 2.2 pounds1 quintal = 100 kilograms = 220.46 pounds Cubic Measure1 metric ton = 10 quintals = 1.1 short tons

1 cu. centimeter = 1000 cu. millimeters = .06 cu. inch1 cu. decimeter = 1000 cu. centimeters = 61.02 cu. inches1 cu. meter = 1000 cu. decimeters = 35.31 cu. feet

Approximate Conversion Factors

To change To Multiply by To change To Multiply by

inches centimeters 2.540 ounce-inches Newton-meters .007062feet meters .305 centimeters inches .394yards meters .914 meters feet 3.280miles kilometers 1.609 meters yards 1.094square inches square centimeters 6.451 kilometers miles .621square feet square meters .093 square centimeters square inches .155square yards square meters .836 square meters square feet 10.764square miles square kilometers 2.590 square meters square yards 1.196acres square hectometers .405 square kilometers square miles .386cubic feet cubic meters .028 square hectometers acres 2.471cubic yards cubic meters .765 cubic meters cubic feet 35.315fluid ounces milliliters 29,573 cubic meters cubic yards 1.308pints liters .473 milliliters fluid ounces .034quarts liters .946 liters pints 2.113gallons liters 3.785 liters quarts 1.057ounces grams 28.349 liters gallons .264pounds kilograms .454 grams ounces .035short tons metric tons .907 kilograms pounds 2.205pound-feet Newton-meters 1.356 metric tons short tons 1.102pound-inches Newton-meters .11296

Temperature (Exact)

°F Fahrenheit 5/9 (after Celsius °Ctemperature subtracting 32) temperature

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